If it wasn't for the penalty to LB for the same class, a 2x SMN setup would actually be kinda neat. Rotate Ruinations would actually lead to a DPS boost, whether it's significant remains to be tested.

My biggest pet hate right now is simply Bahamut himself. Wyrmwave needs to be adjusted to simply being auto-attack upon your selected target. This alone would solve the general clunkiness of using GCD/instant casts just to spit out as many wyrmwaves as you can, instead being able to follow your rotation and maximise use of pre-contagion into Demi-bahamut then Tri-disaster to begin 'Operation Ruin', with the 2 En kindles in between.

That would, in my opinion, go a long way to solving some of their issues, at least for the moment.