I have 10 or 11 HPR and 3 Mana regen, so regens aren't an issue. I also "joust" it, where I hit it, keep running, and turn around for another pass. At that rate, I can get an Armor ignore every pass, for about 6-8 passes, then start beating it down once its breath is survivable. And this is on a melee character where 200 points are tied up in Cart & LP. I used to be able to use the same tactics on Ancient wyrms at level 6 maps, with another dragon slayer, before they buffed the AW at the same time as the introduction of the Greaters.