Ya. I have had a hard time reconciling "we need these extra +s" with "our 21st level party just wiped the floor with Orcus". What gives?
I always felt, when people first raised the arguments about the 'broken math' in 4E, that falling behind by a few numbers would be more than made up by having greater resources (more powers and money for consumables), along with many non-numerical benefits from feats, paragon paths, items, etc.
From what I've seen... that remains the case. I've got a six-person party about to hit level 29. No leader among them. But they have a very easy time getting Combat Advantage (via prone, daze, invisibility), they have powers that reduce defenses or grant vulnerability, many powers that reduce attack bonuses (via rattling, fear, etc). They haven't specifically gone hunting for such powers, but they have picked up enough that it easily makes up for everything else. And instead, with the presence of Expertise, the optimized characters occasionally hit enemies on a 2+. The Epic defense feats have been just as bad - we had a Sorcerer who has various powers that boost his defenses and help him avoid getting hit. Previously, his weak stat - Reflex - could still be regularly hit. Add Robust Defenses and Epic Reflexes, and that's no longer the case.
Now, the argument is that non-optimized characters need to be effective too. But all Expertise does is make it
more likely for a non-optimized character (who doesn't know that Expertise is a must-have feat) to fall behind. Since in order to present more reasonable challenges, Expertise forces the DM to present higher level monsters.
In the end, you can look at the actual numbers all you want. The problem is, that completely doesn't take into account class features, feats, paragon paths, epic destinies, magic items, or the greater benefits and options presented by high level powers.
There might be some room for the math to be adjusted. Perhaps with non-AC Defenses. Perhaps.
But I'm a firm believer that the math was much more solid to begin with, and adding the overpowered feats in PHB2 weighted things in favor of the players - such that the MM3 had to boost monster damage to bring it back towards a balance.
Don't get me wrong, the game still works, with or without the feats, with or without the new damage guidelines. But I continue to feel that Expertise was one of the biggest mistakes in 4E, and that looking at the numbers alone really doesn't provide the full picture.