The first Magnus defeat in Normal Mode

After playing TERA for a while, I'd say that in a game where you can actually dodge or block reliably, monsters that can 1-2 shot are not that big of a deal. And endgame in TERA is full of those. I'll say again, potion cooldowns should be in MS, but only if they fix a few core mechanics with collision detection and hitboxes.

If you actually think that Maple would add real Block and Dodge mechanics at this point...

That's something to expect in MS2, but since MS2 isn't going to be 2D...