I use Cover alot when helping low level people in the lower dungeons that I can use it in. Sort of a safety net ability to allow for mistakes.

My most amazingly fun use was in ExBug. The team slowly wiped and at the end Rav had like 1-2% health left. The WHM and I was all that was left. He finished the MT and turned on us, so I figured why not and ran to the healer and hit cover and HG and we used those 10 seconds wisely and beat him. After that I was like... "wooooo! That was fun!"