Anything like Revenge of the Enemies? http://www.nexusmods.com/skyrim/mods/40491/?

Revenge of the Enemies adds things to make enemies use better and varied spells, racial abilities, dual wield, blocking, varied shouts, etc but there are a lot of reports of this making the game insanely difficult.

http://www.nexusmods.com/skyrim/mods/27866/?, perhaps, and http://www.nexusmods.com/skyrim/mods/18436/? for giving enemies more spells (from mods as well, such as Apocalypse), more perks, using potions etc.

I use HLE thanks for the ASIS tip

Revenge of the Enemies looks so good but "one hit kill enemies" is unacceptable with Skyrims flawed blocking mechanics.