Honestly, I think DRK will be a class from the start with 2 classes to pick from. It's just my opinion, but I think those classes will be MRD (some tanky skills) and SMN (and not THM). Again, just me, but I think DRK's mechanics will be in debuffing hte enemy to mitigate damage, rather than overwhelming defense or massive HP. Things that slow the target or reduce their damage output and SMN's miasma/bio stuff fits that bill.