As Grimiku pointed out in the an earlier post
, one of the things we want to avoid with the reward structure for Monster Power is creating a situation where players feel forced to run on the higher levels, even if they happen to feel more comfortable at somewhere between MP1 - MP3. Ideally, the added challenge should be the primary motivation for how you select your MP level, with the bonuses simply being a really cool perk that you get in return.
On the flip side, though, we know that lot players currently feel "forced" to run on the lower MP levels because it's more efficient to do so (especially if you're looking to farm XP). That's not a great situation either. So, while we don't want to change up the entire reward system for MP, we do agree that the XP bonuses could be more enticing at the top end, and we're looking to make some improvements.
I don't have a lot of details for you right now beyond that, but we've definitely heard your feedback and are trying to incorporate it in a meaningful way.