Grimoire just shows repetition to be honest. There isn't one card that requires any skill to obtain. All pvp related cards can be boosted and all pve cards are just grinding for kills. In the same sense I had 3 runs last night asked for 315+ and finished all within 1 1/2 hrs each. We had a lot of trouble on oryx on the third run but we did have a 311 that kept dying at oryx and for some odd reason really struggled with warpriest. Once the person left at each section and was replaced we finished that section quickly. Sure 315s can be carried but high grimoire can be boosted.