Before anyone says Shield of Condemnation (which can lower fort by 50%) or Improved Sunder, Shield of Condemnation, I'm told, lasts 20 seconds. In order to get the enemy fortification lowered by 50% percent (and the math is not well known. Does a 50% fortified mob get lowered to 0%, or 25%?), a supposedly 5% proc chance must proc five times within 20 seconds, before the timer resets. The only boss with enough attacks per second for this to be reliable is Queen Lailat, who doesn't have very high fort after the update, anyway.
This is incorrect. Every time Condemnation procs, the stack increases and the 20 second timer will restart. It's a 10% proc chance on taking damage.
A 50% fortified monster with a -50% fortification effect will be at 0% fortification.
Improved Sunder is more consistent, but elite devils have seriously high fort saves.
It has stacking fort save reduction attached to it, even on successful saves. If you're still having trouble landing it after working that stack up to -15, there are several ways to increase the save DC. (Shatter weapons, higher strength, Kensei, various Tactics enhancements.)
Shintao monks can also use Jade Strike on devil bosses to lower their fortification by 25% as well, on a failed Will save. That's a bit tougher to land though. Against non-devil bosses, the dark monks have Touch of Despair available for 25% (and Improved Sunder makes it more likely to land). Opportunist also reduces opponent fortification by 10%, but that's personal only.
50% fort was fine and didn't marginalize any particular class to the point of uselessness.
Every Pit Fiend and Horned Devil raid boss' fortification is currently 50% on normal, 65% on hard, and 80% on elite. Epic Velah's fortification is 50%. Epic Lailat's fortification is 80%. Even the Lord of Blades left his heavy fort item at home, and is sitting at 80% (even though he really should have the Improved Fort feat).
If people are working together to reduce fortification, those numbers are able to be significantly lowered or even reduced all the way to zero, and all of the physical DPS goes up.
The idea is to make sword-and-board tanking viable, or even required. That's why they raised the boss damage to 120-150 a tick, also.
There is a strong desire for tanking characters to be welcome in more difficult raids. The Lord of Blades and Master Artificer encounters were built with this in mind.
We also like things like Improved Sunder and the other active fort reducing attacks having value. Currently Condemnation is the biggest single source of potential fort reduction, but it's less reliable than the active attacks.
We want to encourage teamwork for these high end encounters when possible. It's a sacrifice for me to take Improved Sunder and use it, but it helps everyone. (Even the guy casting Disintegrate.)
Fortification affects classes differently, that's the real crux of the problem.
The increase in fight length is the part that casters have a tougher time dealing with than melee, since melee characters don't run out of gas in the same way.
The whole increased fort issue is really sad for rogues, considering we don't have ANY way to decrease it (i still believe opportunist doesn't affect SA, only crits).
Opportunist should improve sneak attack percentages on creatures that are not inherently immune to them. (Undead, elementals, etc.) At this time it does not permit sneak attacks on sneak attack immune opponents.
Edit: After doing some investigation, I can confirm that there is indeed a bug with sneak attack and opportunist. It's not always being applied correctly.