Quick update on my situation, i had pretty bad gpu usage and the core was down clocking before, i tried everything with only minor improvements, i had no issues with the original install but decided to have another crack at re installing 14.1.
With the second attempt i got a yellow question mark thing in ccc but no errors, still had the same old issues tho. Booted to safe mode , ran driver sweeper, re installed again same issues.
In the end it took about 5 try's but wowee, the result was worth it. I believe the install that completed properly for me took a tad longer than all the others that had issues (even tho some of the attempts reported no problems) I now don't get any fluctuations in bf4, for gpu usage it stays at 100%, for core clock it stays at 1080 which is all i have it set to atm, ZERO fluctuations. It is soooo damn smooth. Compared to what i initially thought mantle was this is crazy good.
My advice is that the gpu usage and core downclocking issues aren't a bug with mantle or this driver that need to be fixed in a later driver by AMD but a issue with the install that can be rectified by us with some persistence.