I wouldn't mind if the game consistently ran at say 25 fps if I lock it to 30 or 55 fps if I lock it to 60.
What drives me to the point of insanity is that regardless of where I lock it, it randomly stutters down to 25/55 for a second then back to 30/60 when I'm walking around. I just can't deal with that.
Perhaps you just need a better framerate limiter? At the risk of shameless self promotion, the limiter I wrote for Tales of Zestiria and Fallout 4 is included in Souls Unsqueezed.
http://steamcommunity.com/sharedfiles/filedetails/?id=663922936
Even if you don't need aspect ratio correction, it has a pretty sophisticated limiter that avoids hitching. I'd encourage you to try different values for TargetFPS in dxgi.ini.
I run the game at 4K locked to 48 FPS and it works very well on my 3-way GTX 980 system (2 of the GTX 980s are disabled because input latency was annoying me).