The issue isn't really whether Muslims are too strong or not. The balance you're looking for is impossible, since if one side has even the slightest advantage, they will inevitably landslide over the other as the RNG determines.
The only way to fundamentally affect the nature of the Muslim blob vs Christian blob phenomena is to make the provinces more difficult to conquer. It's very easy to conquer a province when you just swoop in, siege the capital, and boom, it's all yours, with all the baronies and bishoprics or towns, with 100% warscore.
The only way to fundamentally affect the nature of the Muslim blob vs Christian blob phenomena is to make the provinces more difficult to conquer. It's very easy to conquer a province when you just swoop in, siege the capital, and boom, it's all yours, with all the baronies and bishoprics or towns, with 100% warscore.