No such thing as a bane prepatch really. Only thing you have to watch out for is if early in patch 97 they bugged out their bane dragon and it's 4 slot. It should be three slot.
Nightmares will have 295-315 hits and 495-525 strength and will be 2 slot. If it's 315 hits/515 str you would want to take perhaps extra precaution as those are ones from prior to publish 16.