Current trends run toward greater dragons.
That being said, I prefer to use my rune beetle/bake kitsune combination. They kill things much more quickly than greater dragons.
But it's all situational. There are fights where the cu sidhe is the best, fights where the greater dragon is best, and fights where the beetle/bake are best (I've used all three in the last week on the new invasions/quests as well as a pair of bake kitsune and a pack of frenzied ostards).
I still see people with the nightmare/wyrm combo, but I haven't even tried it myself.