The Glavenus isn't THAT bad, it gets predictable after a while, I didn't even have to dip into my mega potions when I fought it, though I have to admit to start it's pretty intimidating, I've noticed though that my main way of fighting just involves me keeping my distance for the most part. I wouldn't say I enjoy fighting it though I'm not super fond of it's armour set either. And I also got it at release and I'm HR3 with low rank mizutsune armour