I would say, raise the cap, but the casual and hardcore aspects have to blended perfectly in the 1-50 range, you can't hardcore players and casual players divided between level caps, the casual players will want to get to rank 51 in a game they play and would find it too hard for them at 51.

Also a huge assumption that may be wrong here is that hardcore players don't want mid level content and casual players don't want endgame. I think both groups here want the same thing, the argument is how. They're has to be a balanced mid-high rank content and endgame in place to appease both these groups, not two separate systems. That's why this is so hard.