Changes in MM creatures - why?

[(Psi)SeveredHead]

I like the new hydra. I think it puts to rest Whirlwind Attack or Great Cleave cheese to kill hydras (I don't know - can you Sunder more than once per round?) and it's hard to Sunder a hydra because of it's high attack bonus (while it's easy to lop off it's head in 3.0 due to it's low AC).