Tessellation is very hardware intensive as it subdivides the surface into more pieces to render. (Vertice Point/Triangle/Polygon Count, Tessellation, Dynamic Lighting, and Particles have the biggest impact on performance, it’s always been that way as far back as I can remember.)
Are you using latest video card driver?
A few years back even the monitor refresh rate, vertical sync, motherboard PCI Express bandwidth throughput (the speed at which the data can travel throughout the motherboard to get too and from point A to B like for processor and memory.), and power supply could impact things (such as lower framerate due to insufficient power to the video card to fully power it or to match AMP requirements to keep hardware from burning out, etc, etc…).
Some think R9-270 and GTX 970 250watt power requirement is the same with a LGA 1150 compatible processor stock and attempt to power that with a 300 watt power supply, but what about the rest of the computers power demands? It’s too risky with the those video cards power spikes. A power supply at 630 Watt - 700 Watt with Gold or Bronze 80+ rating would be better, that wattage value isn’t what it’ll use, but rather what it can output if it needs too depending on power consumption demands of your computer and all it’s plugged in hardware. I don’t know what your power supply but that’s something to consider if you are running higher end Full Sized video cards.
Check in Wireframe Mode.
Use the viewing tools to check for visual performance issues.
Many things impact performance, have you tried adding a Lightmap Importance Volume and doing a Full Build?
Checking your lighting settings?
Have done that and checked the screen resolution and set the MaxFPS and FPS Smoothing values then tried it stand alone to see if there’s a difference? (Aka Manually adjusting the framerate settings?)
Have you setup proper LOD distance range?
Backface Culling On or Off?
Is it trying to render geometry as double sided instead of single sided?
Changing any of the scalability settings?
Tessellation:
http://www.nvidia.com/object/tessellation.html
Unreal Tessellation Documentaiton:
.unrealengine.com/latest/INT/Resources/ContentExamples/MaterialProperties/1_8/index.html