As a pure warrior tank with 550 def, 24% dodge, 19% parry, and 21% block, I do believe this is still a bit excessive. Here is a better idea...instead of nerfing everyone's dodge (remember, it WILL affect rogues' dodge as well - making them totally ineffective in ICC and other instances), how about instead removing the previous dodge and parry nerfs and instead nerfing the abilities of classes who you don't need to tank? While I understand the need for this given DKs and Druids using super dodge to currently tank, I don't understand why it has to be 20%. Why not instead remove their ability to properly tank and instead improve their dpsing? Finally, if you reduce the damage multipliers for massive hits, you remove the enemy's element of shock and surprise to those players who NEED to learn how to fight a raid or instance boss properly.
I have seen a bunch of silver spoon T9 geared kids think they own the world with their awesome gear, even though they don't know how to use the proper rotation and/or strategy on a boss because they have worked the entire system to their advantage. Please don't punish those of us who follow the proper talent combos. Instead, find out where the real problems are and fix them. Thank you.

Speaking as a healer, I'm totally fine if Blizzard shifts from Dodge to lower damage. Part of what makes avoidance so attractive is bosses that can two-shot tanks. If we see a more steady decrease in health, it'll give us the precious milliseconds to see and respond, without having to second guess the boss.

Particularly as a Disc priest - lower damage makes the shield more effective. Bring on the blocking, Blizz. ;)

Yikes. I know my own dodge chance at the current moment, in my set focusing on the stat, is only around 22%. But then again, I'm not in full ToC gear either. So we'll have to see.