Been asking it for years so maybe I should make a shot.

Sura's Dispel skill can be used against monsters, if the effect is successfull the mob will only have the dark cloud. But does the mob somehow get damage loss or anything he get lost?

And secondly, as Dispel cannot be used on high level players, this also includes mobs?

I know for a fact there used to be a glitch with Dispel that when you use it against bosses and it worked, the boss never did its skill attack. Therefore he never made a high damage attack and you could beat it easily.