I still don't get what the fuss is about. Near as I can tell, Tumble is already less than awesome. I sometimes cut it from tight builds (three skills for detections, two for concealment, disable device, open lock, UMD, knowledges, social skills, etc. usually get priority), and many builds don't work with it because of armor penalties, and even then it doesn't always come up and it may not save you from much if it fails. I see no reason to nerf it from a balance perspective.
From an in-character logic perspective I see even less reason. Tumble lets you move without dropping your guard. If an enemy can't just ignore your guard willy-nilly when you're standing still, and if you can hold your guard just as easily while moving as you can while standing still (which is why you put points into tumble in the first place), it's utterly ridiculous to say "You suddenly forget what you're doing and get hit, because it doesn't make sense to let you do what a level 1 commoner couldn't... well, yeah, even the commoner could have defended well enough to not provoke an AoO had he been standing still, but you still can't learn to, because your legs are moving and you can only operate two of your limbs at once when looking at a dragon."