As I progress through the game, low tier mobs are more of annoyance than even tiny bit of challenge. And to get rid of that annoyance without removing mobs altogether, I can think of mod that introduces fear based aggro system. Each armor and weapon items player currently wearing has it's fear value, and each mob has it's negative fear value and fear threshold. Each enemy looks for other enemies nearby (in some radius), all their negative fear values adds up with players summary fear value and the resulting value compared to fear threshold, if it's greater – mob will flee, or maybe try one or two distant attacks and then flee. Or, as a bit more complex behavior, he could check if there's other enemies nearby (in some radius) and if there is, he could flee to their direction, so they could eventually reduce fear value below their threshold.
With large groups of enemies with such mechanics it'll be possible that smaller creatures would flee (greylings, greydwarfes), while larger one (or stupidier ones) (Trolls, shamans, brutes) will try to fight player and die, whether fear value is in between that small and large creatures threshold.
Such mod should greatly reduce annoyance from that pesky little greylings (though, they still would be annoying, as they still could break things around), at the same time keeping game's immersion and lore.