if its like any other spells, you cant dodge while casting. so the dodge stuff too. you are the ultimate squishy while casting.
but they hit for 300. 450 if you want "unmitigated" due to the 0 armor. at level 80 you can get a full set of "of stamina" gear (since any dodge/armor will be wasted anyway, just go max health). And I'd presume you would easily be able to get to 20K ish hp (in that type of gear). if they hit for 500 every 1 second you'll have 40 seconds to get your tame beast off assuming he hits you every single time.
at 80 i'd hope more than 20k would be possible on a hunter.
since its possible for a hunter to get close to 20k hp on retail (lots of sockets xD and pvp gear)