I’ve just tried to look up the specs of this processor - Intel ARK doesn’t recognise an i5-3250k in their database. There is an i3-3250 if that is what you are referring to?
If you have ever manually edited your Dirty Bomb .ini files, deleting them and allowing DB to create fresh ones can solve a great deal of problems between updates. We generally don’t recommend editing them for this reason.
That said, here’s a few other things you can try…
First, you may want to head into “Power Options” and select “High performance” from the plans listed - if your CPU is being power throttled, this should eliminate that as a potential bottleneck. If you have a third-generation Intel i-series, you’ll want to squeeze out every ounce of power you can from it.
You will also want to make sure you have the latest GeForce drivers for your GTX970 - this card is more than capable of running Dirty Bomb (I used to have this card myself).
If those quick tips don’t improve things, it would be really helpful if you could submit a support ticket and send us a copy of your DxDiag so we can look into things further.