I'm leveling a paladin atm and have found a nice way to cut mobs in half before even reaching me.
HoR only deals damage if the mob isn't attacking you, and exorcism has a 1.5s cast time; however, I found that if you cast Exorcism and immidiatly hit HoR; HoR will also deal damage!
-300HP headstart, non crit; top that with a judgement and you're halfway there!
Reason this is an exploit is that Exorcism isn't a missile spell so when cast it should immidiatly hurt and aggro the mob, causing your HoR to do no damage; but for some reason it does. ^^