I think more Vanguard vendors is the real solution. The problem doesn't seem to be that Crucible marks are no longer available to PvE players, but that there are a lack of options, which makes the Crucible vendors desirable. I don't see how a mark cap increase is relevant. There are many options for Crucible marks now, but no cap increase for those marks. I would love to see PvE-specific perks that are a little off the wall, since balance is a little less of a priority. Armor that zaps back melee attackers, overshields, crazy weapon perks... All isolated to non-Guardian targets.