It sounds to me like you need a bigger or better tiller to work all of the mulch into the ground. My Troy-Bilt does an admirable job. I till in leaves etc. in the fall until no more will go into the ground completely. Then in the spring I ad even more stuff and till it in until it is gone. I am now in sand and you can never get too much mulch tilled in in this light soil.And when the crop is done taking all the mulch composting it,instead of working it in the ground to keep from looking so Trashy.
Just a thought, hope it helps. The same method worked well when we used to live in heavy clay soil also.