My 2cents.
First off, I also noticed a definite increase in gain when upgrading from 13.07 to 14. I play mostly clean, and mostly through the same patch based on the Vibratoverb but I also noticed the jump in my higher gain patches. Whereas in 13.07 the tone would break up only with harder, more dynamic picking, it happens immediately with 14.
That being said, I'm pretty sure I know why people get so concerned about this because I get the same thoughts myself. OK, it's fairly easy to reduce the break up by adjusting the input drive/trim and then maybe increasing the level to add some volume back. But the thing I always worry about is what is the cause of this increased gain? If it is simply a side effect of improved modeling technology then so be it, no worries. However, (and this is the real worry) I wonder if one of the other parameters somehow got reset (increased) in the upgrade process, say for example speaker drive, or Xformer match, or one of the compressor settings etc etc? If that happened, simply reducing the input drive/trim is just masking the effect, and the actual tone of the preset has changed forever. Now the problem is, without laboriously recording and cross-referencing each and every parameter in each block you would never know if this is the case, hence the niggling worry that eats away. Does that sound familiar to anyone else?
One solution, and I don't know if this is practical, would be to develop a diagnostic tool, maybe as an add-on to axe edit, that could take a snapshot of all preset settings both before and after FW upgrade and then compare them and highlight any changed settings which could then be reset to their original values. I would find that very useful and reassuring and could be used for other purposes as well. My first thought whenever a patch feels or sounds different, not just after a FW change, is that some obscure parameter has changed somehow with my being aware of it. It's just a thought.
Of course, if none of the actual settings are altered during the upgrade process then this is meaningless.