The only other really big thing I've noticed that messes up my success is the "threatened" status, which is nasty for casters, but particularly frustrating for melee fighters because of course they're threatened, they're fighting in melee. But I digress, if you are threatened (a hostile is within arm's reach) you are, in theory, so scared or in peril or whatever that you mess up your spells and attacks, pushing and jumping are useful here too
Threatened should have absolutely zero effect on a character using a melee attack.