A fair amount of Heroic trash is immune to hunter CC as well, be it scattershot/freeze/frosttraps, conc shot etc. Pets can tank okay up till outlands but even the lv70 mobs can tear 'em up, I don't wanna imagine multiple trash mobs let alone a boss beating on them, even rotated they'd go down quick. My 21/40/0 Hunter's Boar is decked out in sta/armor talents and while he can take a little beating he ain't no instance tank post-bc(though he DID offtank things in aq20 quite well, and a guildie's full-BM boar pre-bc MAIN tanked Onyxia without any deaths lol)