Yeah I don't know what NTL was thinking giving Shadow Knight's all that support and leaving Dark Warriors with AoEs that don't do much damage like they should.
As for Cranes, they also have buffs to make them more bulky and resistant to debuffs. They also got a nice, heal skill that can be used on teammates. Of course Turtles have a Hitrate buff as well as an AoE Stun, but again I believe this is more a person's preference than anything.
Please note that I'm talking about PvE.