"I don't really understand why hamstring and pummel had their damage removed. Then again, Shield Bash had its damage increased and improved shield bash will now increase the damage of all those shield slams all warriors will be doing, so your guess is as good as mine as to why the change."

I bet Hamstring had it's damage removed to make blocking more useful for people with low-block-value shields(newbies in pvp). Nothing more frustration than BLOCK! while trying to pin down a shaman, paladin, or warrior.
Shield bash likely had it's damage increased to punch through blocks so you can proactively silence, and to increase protection solo viability. Arms and fury warriors are getting Shield Slam, it's only fair that Protection warriors get a weak form of Bloodthirst. There's a big push towards tanking and protection abilities scaling with attack power: thunderclap, shield bash, concussion blow, and now shockwave too.
The change to pummel is anyone's guess - I wonder if rogue Kick will go the same way?