MRAPs are a huge mixed bag. They're very expensive, don't fit on ships, and cost an assload to maintain, despite the bulk of them still being under warranty. Not to mention the more common operational issues they have, like getting stuck in sand, having pedals shear off while being driven (that was fun), and being stupidly top-heavy for all-terrain use. Oh, wait. That last one is a 7-ton AND an MRAP problem.
Sure, they're like RVs inside, and the armor is nice. But is the tradeoff worth it? I'm not sure.
I thought the JLTV was the new wave of the future, and that the Marine Corps wanted to move away from this kind of thing?