DunedinDragon

First things first...TURN OFF YOUR GLOBAL EQ.  Let's get that out of the way right now so it's not confusing the issue.  If you don't know how to do it simply hold down the BYPASS button for a couple of seconds until the little rectangle graph next to the Snapshots icons disappears.  This way you won't be worrying about global eq affecting your sound.
Next get a DECENT pair of headsets and listen to your patch.  If it still sounds thin, check some of the factory presets and see how they sound to you.  If those are sounding okay through the headphones the issue is how you have the amp output setup.  If the factory presets sound okay but your preset doesn't you've got something messed up in your preset.
There's really no use going any further until you've figured out where the problem lies.  There are some good recommendations here, but everyone is still guessing at how you have your sound routed so it's best to settle that first.

I think this conversation is getting wrapped around the axle because it started off with a somewhat faulty idea of how to fix a problem.
 
First off, it's important to understand the control over the signal you send out the XLR to the FOH is pretty much irrelevant given that the mixing board has complete control over how much signal it receives via the gain or trim knob on that channel.  As long as you're sending a non-clipped signal in a form the board is set to receive, that signal can be gain staged at the board to an apporopriate signal level.  And the typical signal most boards are prepared to use on XLR inputs is Mic level, although line level is also acceptable in some cases.
 
So the easiest way to fix your problem is to configure your system so that the Master knob on the Helix only controls the 1/4" out, and the Master does NOT control the XLR out and the XLR output is set to Mic level.  Then you can dial in whatever volume you want for your stage monitor and the signal being sent to the board will be a consistent Mic level signal that only has to be gain staged once during sound checks to the level the sound man wants.  That is actually the most important purpose of soundchecks.and if your sound man doesn't understand how to do that you've got a LOT bigger problems awaiting you for that gig.
 
As long as all of your presets/snapshots have been normalized to have the same relative volume and you're not adjusting the Master output for different levels on presets/snapshots, this configuration will work fine/

Check your USB settings in Helix global input and outputs.  Sometimes the value for USB 1/2 gets munged up when upgrading.  Mine did.  Once I set it appropriately everything was fine.

I think most of us use our 1/4 L/Mono output to go to our personal stage monitors and then use the XLR L/Mono output to go to the board.  There are several reasons for this.  First, XLR is the preferred method for going long distances since there's less likelihood of noise or interference on the line.  This makes more sense as your distance to your stage monitor should be quite short.  Also sound boards are normally designed to use XLR inputs.
 
The way I set mine up is I configure my 1/4 to use the Helix master volume at line level, and the XLR to not use the master volume and use a Mic level signal in my global settings.  I run a short 1/4" output cable from my L/Mono 1/4" output to my DXR12.  I use a phantom power blocker on my L/Mono XLR out to a XLR cable to the board.  This ensures I don't affect the Helix if phantom power happens to be turned on for my channel at the board.  This setup also allows me to control the volume to my stage monitor (using the Helix master volume) without affecting the signal that goes to the board.  This makes it much easier for the sound personnel to keep my signal mixed appropriately.
 
I personally use a full Helix floorboard.  Of course when I bought mine there was no Helix LT.  But I did end up buying a second full Helix floorboard even after the Helix LT was introduced as a backup unit as well as an interface to my DAW and recording environment at home.  The main consideration really is the additional inputs and controls that drive this decision.  In my case I use the Aux input for my acoustic guitar.  I also use the input loop for my keyboard occasionally.  The headphone output control is an absolutely essential feature for recording.  The other main consideration for me was the durability of the full Helix.  It's simply built to take more punishment...not that I'm all that hard on my units, but I really depend on this thing week after week and can't afford to be babying it.

I get this all the time with my Yamaha DXR12.  I have a two outlet strip that I use for both the Helix and the DXR12.  I wouldn't call it a loud hum, but it's definitely there if the Helix is off.  It's never affected anything in a year and a half, so I haven't bothered with it.  My guess is it has something to do with ground inequality within the switch if one of the units is turned off.  It does the same thing at home with both units plugged into the same power strip.

It's clear something in the OS is having problems with loading/managing device drivers.  It could be the USB or it could be some problem with memory or memory management or memory infractions caused by interactions with something else you have loaded.  Either way it's a problem specific to your PC's setup as what you're experiencing isn't a common problem at all.
 
I'd start by looking at the Windows event log when something like this happens and that might give you a first clue as to where to look.  You might also look at the event log to see if there are any errors or warnings when you turn on the Helix and the devices get loaded.

Once again, this has nothing to do with Helix.  It's how Windows works when presented with a new audio driver.  It works this way whether it's a Helix or any other USB audio device that gets plugged in, and it works that way for everyone.  Just do as AlexKenivel recommends and disable the Helix device as a playback device in your Windows sound settings.  There is NOTHING you can do on the Helix side because the Helix is just doing what every other audio device does when it gets plugged into Windows.

I personally use the DXR12.  A lot of folks however are happy with the DXR10.  My decision for the 12 was simply the fact that I've always been happier with cabinets that use 12's rather than 10.  I suspect it's the fact that I prefer a bit warmer tones.

That sounds like a very reasonable thing to do in my case.  I may have to do that each week for a while until I work my way through all the presets, but it's a lot better than loading them all up.  Thanks a bunch!!

You're not alone in this, but apparently people like us tend to be in the minority.
 
There's a lot of metal guys using this gear, but if you have the patience you'll find you can get exactly the tones you want.  But you'll probably end up building them yourself..that's what I had to do.
 
This isn't unusual in the modeling world.  Prior to getting the HD500x I was using a Mustang IV which has many of the same type of features as the POD.  It came with all sorts of presets that were totally useless to me.  So I'm already used to dumping the presets that come with it and building my own.  You can get a jumpstart in some ways if you want to download other user's tones from CustomTone, but in all likelihood you'll end up having to modify those as well because they were built with different guitars/pickups and used on different amp or FRFR speaker setups.
 
How many of these presets you choose to build for yourself is really up to you and your needs.  Some people are happy with 4 or 5 different presets that cover the range of clean to overdriven and everything in between.  As for myself, I enjoy building my own presets and because I use several different guitars depending on the song, I just build a preset for every song in the band's repertoire.  Many are very similar, but have some minor tweaks.  But it makes it easy for me to build a setlist because I have one set I names "Performance" and I copy the presets from the set I named "Base" into the appropriate slots in the Performance set when we perform.  I also know that each song will sound closer to the sound I'm going for whether that be Eric Clapton, Queen, Chet Atkins, The Beatles...whatever.
 
It's taken some time to get this all done, but it wasn't that bad...and it was a really good way of quickly learning the ins and outs of the POD.  Right now I have roughly 58 of my own custom presets I've built over the last 5 months.  And that was starting from scratch not knowing anything about the POD.
 
And believe me, you're not too old.  I'm 63 and I've had a blast learning this stuff and building presets.  It's better than spending my time on a coin collection...   B)
 
As far as the presets that came loaded with it, I just saved them off to the PC's hard drive using the Edit program.  They're there if I want them.  And then I just write over whatever preset I want to use.  Personally I just used the last two setlists on the POD for my purposes as that's what they're kind of meant for.

Yes, the physical EQ knobs equate the the knobs you would normally find on an amp.
 
There are a number of reasons why you would use digital FX EQ's depending on the effect.  For example, the EQ knobs for the amp are somewhat wide scoped in frequency range and vary from amp to amp.  In some cases you may want to accentuate or deaccentuate a certain specific and tighter range of frequencies within the frequency range than what's set by the amp, so you might appy one of the many, various parametric or graphic EQ FX at the end of the signal chain.  In another case you might want to change the tone when you kick into a lead, so you would adjust the EQ knobs on a boost or overdrive pedal to get that effect.
 
Basically the EQ settings on many of the FX are there for fine tuning, but they will all be subject to and affected by the base EQ set on the amp.