Why unit upon height/cliff reduce FPS a lot? (esp. w/hp bar)

[SamNainocard]

This maybe sound weird, but I experienced that once lot of unit is upon height or cliff it will reduce FPS a lot!

Let's see...
First I try to use initially cliff (at 2) I almost same as no unit, FPS always 60-65
But once I try to lift up a cliff for example, well, now FPS is reduce to 39 when showing health bar. (about 55 FPS without health bar)

See my image for little example.

Image

No Cliff

with Cliff

This maybe a little problem but with map like Darkest Hours of Guardians, its reduce a FPS to 25 or less...

Any solution?

 

[ap0calypse]

Don't use cliffs, but use the terrain tool to make it higher?
Don't know if it helps tho

 

[SamNainocard]

Nope, as I said, it's both Cliff and Height (title said).
In image which use cliff is just quick referring.