There are no titles in World of Warcraft-which is basically where the achievement system came from, especially the titles-that rely on RNG. There are [i]achievements[/i] that do-off the top of my head I can think of one that requires RNG mount drops to complete-but as far as I know, there's no title that requires an RNG drop to get it. And especially not the RNG on top of RNG that is Dredgen. That'd be like telling a WoW player that they needed to kill the Lich KIng [i]and[/i] a rare spawn [i]and[/i] hope that it drops rare items to get the Kingslayer title for killing the Lich King. That's dumb.
Dredgen? Huh! Warfarer and BrayTech Weapons look and dredgens with conviction.