I feel that I will get some flack from this but I want to show this anyway. I have a Shadow Demon and have found it to be a fair amount of fun to take him into situations and let him "handle" them on his own. Here is a link to a video (I know the quality could be better..) of him doing a 5 man HE in our stronghold. I will post more soon. Give this a try with your pet and let me know your results.. I bet there are other pets that can kick butt as well.
https://www.youtube.com/watch?v=aKmkJyOIZX4