Oh, no I think the mechanics are fine! It's a little hard to make sure you get to position characters where you want them and it's more difficult because you don't activate the secondary abilities of characters you switch to by reflecting off the edges of the screen, but I think that complexity is a big part of what makes the game fun.
I do think that having to choose between healing and levelling up makes the game a bit exponential in that if you do well early then you will have stronger characters and be able to do better later but if you have to heal then the game will become even more difficult for you, but that kind of progression system is pretty popular right now, even if personally I feel like it means you have to restart until you perfect the first couple levels and only take level ups till you are maxed out XD;;