It always kinda bothered me that when I did a large horizontal sweep with my two-hander the person almost directly beside my target was never effected. Then with FCOM installed getting swarmed seems to be a common theme so are there any mods that add area of effect to the melee swings or adds a spell/skill that does so?

Well this one has quit a few spells that can do that. Like a spell that rotates magic blades around your character for a while...or noxious fumes that can stagger your enemies...rocks that will toss your enemies a side while damaging/killing them. But it is not a standard magic mod so be warned. (Although it is a extremely good mod IMO. )

http://www.tesnexus.com/downloads/file.php?id=9562