Problem with him is that being 4/4 it's so easy to pewpew 2/2 Gnoll and Argent Commander -> Hogger. There are many 4 damage spells/stuff, so that's the point of swapping for Illidan, who has 5 HP, so he can survive to this attacks and at least do something next turn, plus he's a demon so as a warlock you can buff him (and I think he has the same "go for him like mad" feeling, just they need bigger stuff to kill him).
I understand Hogger can be really dangerous with some classes that can buff/protect him better, but as a warlock that's not really easy :/
Maybe I'm just not getting something, so some tips would be appreciated. But in my situation, don't you think there are better options?