I actually wanted to comment on this too.
Honestly, the whole "squares are more tanky" thing is mostly a load of BS in most cases, and the reality is that most non-squares have a much easier time not getting hit. Wizards are one of the tankiest classes in the game, if not THE tankiest class (520, 530, 535, 540, 550, 414, 430. Seriously, it's almost ridiculous.), and even reduce maneuver damage more than someone in full plate. Few maneuvers are actually deadly, and it usually comes down to raw DS/TD for your survival. There's exceptions, but I find most of those things can be overcome with resists, warrior fittings, and/or crit padding. So yeah, SMR is a pretty lame ass weakness, and they got a huge gift basket handed to them with the SMR changes making them able to dodge them WAY better than before.
Sure, as a spell casting rogue with 100 spell ranks and plate armor, you can be incredibly tanky, especially coupled with hiding. But another class with equal XP is not likely dying much either. The reality is as Methais put it - a lot of the HW stuff is just going to wreck you no matter what your defense is, so it's mostly about disabling them or killing them first.