It was probably the weapon then. He was in Grit (and actually asked me why I had such high enmity gen, to which I answered: "I just push buttons..."), but, at the time, I had the hive weapon and I'm pretty sure he was still rocking the 175-180 Law weapon. So, that must have made the difference.
As for your AoE spam rotation, I'll definitely give this a shot. I'm typically shy on using AD because the Mp cost is so high, but if this works well then I may revise my Mob tanking method. I typically carried over a lot of habits from Pld (rotating targets on primary combo to hold enmity is pretty common and required given the low enmity gen of Flash and RoH), so it has been a learning experience to use AoE spams as a means of holding aggro.