I think they had this back in 1.0 but correct me if Im wrong. Also I believe they took it out due to the bad AI system which isn't that better now. Also don't see much reason to add it other then your history in HW with the brood. Not saying I don't like the idea but I don't think it would be possible. Also you got summoner already having a pet might be a clash in identity if you just give DRG a pet and now with DRk having living shadow its even more of a no, plus reaper if you where thinking that they have a combo system around it. Idk since reaper will be sharing drg gear I cant say it could be impossible but it wouldn't be a pet it would be that just like reaper weaved in with your combos.