neieus :
Either way you decide to go just remember that the GPU usage drops are not CPU related. As previously mentioned search out gtx 900 low usage and you'll find i5/i7's with the same problem. Weak core or not I've never experienced any problems playing skyrim with mods with HD pack installed.
I have heard but can't confirm some GPU drops independent of CPU but that doesn't change the fact that an FX-8350 will bottleneck a GTX970 in most current games.
If so it's likely an issue that will be fixed and may only be in some games.
When a CPU bottlenecks a GPU the GPU won't run at 100% usage as it's left waiting on the CPU to finish its tasks.