It's not a bug. Characters can dodge dark avatar if they see you casting it and run away. The best time to use the skill and get it to hit 9 times is to land it right on top of your enemy while they are casting a skill (and not moving).
I'm sorry that I forgot to mention this in the guide. You should only get max rank after you farmed the purchase points required for the items you want from NPC Lowe. The point of me introducing Crespo Abyss in the guide is if you accidently missed some stats so you can't equip a higher level weapon and etc; but also so people can farm their ranks (at end game) when it takes too long time in dksq. I've never heard about anyone instantly going max rank in Crespo Abyss without doing DKSQ before haha so I guess I never thought about noting that in the guide.
It's definately going to be tougher to get Purchase Points now, but an alternate way to get Squama could also be to grind dils and buy from other players.
I have made a note in the new player guide about this now, so that future new players won't make this mistake. Thank you for bringing this to my attention and again sorry.