Flare, first of all, your current strategy of “Oh, just attack anyone! :D” doesn’t work. It isn’t fun. When I’m a 4ker, and I can get the same rewards from a 3.5ker as I can from a 4.5ker, then I’m going to go with the easiest battle, and it’s not even going to be a challenge.
So here are the things you need to do:
Make skull count based on something most substantial than level. There are numerous threads in this already, so I won’t repeat them.
Base skull count, not only on % victory, but also on time remaining! Ergo, if I beat a base with 40sec remaining, then I should get a 25% boost to that skull count.
What these two things, together, will do is, they’ll make people:
A. Fight opponents who truly are challenging. And,
B. Will reward actual skill. I.e, if you and your opponent have the same spells, then the greater number of skulls goes to he with the best defense and the best raid strategy.