What evenly affects all classes...
Fortification affects classes differently, that's the real crux of the problem.
=0% fort - rogue (esp assassin III) is absolute best DPS by a very very wide margin.
<50% fort - assassin III is still slightly best DPS by a very very narrow margin (mech/acro not so much).
>50% fort - rogue (even assassin III) starts to lose out to barbs/fighters due to their high base damage output.
>75% fort - time to take the rogue class out of your lfm, this now includes elite raids and epic raids.
Any fort % - caster dps DOES NOT CHANGE. So the real question is, if end-game raid bosses (elite/epic) are now 75%/80% fort, why bring anything but sorcs/pm's/fvs to the party?
If you want to raise the fort %, that's fine, but give the classes you are hurting better ways to reduce it. For instance, on my rogue, I took skill mastery twice instead of crippling strike or slippery mind. So why not change crippling strike so that it has a chance to proc a fort % reduction that benefits the entire group. Now, just by adding a rogue to the party (or two or three) you can keep the bosses fort % dropped to previous levels where there was melee DPS balance. If crippling strike applied a 10%-15% fort reduction for 10 seconds and could be stacked 3 times, that would be more than enough to justify bringing rogues into the group for epic and elite raids.
You spanked the rogue's hard with U11, now it's time to come in like a good parent and say, "I'm sorry for spanking you, but you know you deserved it. Here's some cookies and milk, now go back out there and play."