Well, I dont remember what level I was in the previous instances I have run - and I probably was higher than I had to be. However, I did SM Graveyard today with no problems with my team being 30, 30, 30, 29, and 28.

I did WC at around 20 and that went just fine. It can get challenging but certainly doable. As I have leveled I have gotten more and more fun toys and it seems easier to do equal level instances (so far)