Baal crit immune ???

is he crit immune , my hero with crit can NEVER crit on him

Try changing up your runes, look for something that can break evasion, block, dodge. He can be hit with a critical attack, I've seen screenshots and have had a few people mention it already.

I've also heard of someone (posted on the forums) dodging/blocking his attacks.

Yes you can score critical hits against Baal/cerebus. I have done so many many time sin both beta and live.

I have gotten a crit before and Shayd would dodge plenty much with the right rune.

I had like +42 crit with archer at 35 lvl player and have 0 crits vs world bosses.

I have noticed over the past several days I have not been getting any dodge, block or crits on Baal or Cerberus. Prior I had been getting a surprising number, considering the "power" of the opponents.