Your CPU is not the problem (unless it's somehow running at a low frequency which is unlikely).
If the Fire Strike score is correct or close then I doubt you have a problem at all, thus I'd suspect it's your expectations of what you should get are off.
*A different resolution, lower GPU frequency than over 1080Ti's, or some other game setting can significantly change the FPS.
**You should use a tool such as EVGA Precision to put on-screen the following two data points:
1) GPU frequency, and
2) GPU usage
If the GPU frequency is the expected for your overclock (i.e. 1950MHz or whatever), and GPU Usage is high (95% or close) then everything is fine. The graphics card is working about as hard as it can so there's no way to run any faster.
If however the GPU frequency and/or GPU usage is lower then you have two main likelihoods:
a) CPU bottleneck
- run CPU tests to confirm frequency
(even the best CPU can be overloaded depending on the game and settings so a CPU bottleneck doesn't mean a problem... there's ALWAYS a bottleneck somewhere and it can shift from CPU to GPU to storage drive), or
b) FPS cap is set (manually or via VSYNC... that's not what is going on with you though)
But...
I found a video that's a year old where OVERWATCH appears maxed out at 1080p and he got 237FPS average. CPU was an i7-6700K at 4.6GHz so your CPU at 4.2 to 4.4GHz should give similar results... your numbers being different for this game specifically suggest to me it's either:
a) game has CHANGED over time so is more demanding (maybe better lighting or something), or
b) the settings are different somehow
Summary:
May or not be an issue. I doubt it.