I'm going to be looking for a similar rod this year. Last year I used a 6' 6" medium action but found it too light when in the weeds. I lost a couple of fish because I couldn't keep them up and out of the weeds. I also tried a 7 foot medium and it was even worse, and it was hard to get accurate casts. I am going to go with a 6 foot medium heavy spinning rod this year. I think that will be easier to make short casts accurately into cover and around docks and should still have enough backbone for me to horse them out of the weeds. I think your line is definitely not too heavy, 15 pound power pro has the same diameter as 4 pound test mono, so that should not be hurting your casting. I will probably go for either 20 or 30 pound power pro, not for the strength but more for the diameter, its easy to handle.
Those are just my thoughts, haven't tried it out yet, but thats what I am set on.