What do you mean by "proc correctly"?

His A1 has a percentage chance to activate, after which accuracy vs resistance will determine whether the debuff extension applies.

Personally, I have him on my CB team - he's absolutely MVP. I've got him geared in survival stats:

44K HP

2666 ATK

3398 DEF

188 SPD

26% CR

165% CD

198 RES

231 ACC

He's far from optimally geared, but he gets the job done. When I have the time/resources, I'll be trying to get that CR up to closer to 50-60%, and the speed up above 190 for UNM.

My Vizier is fully booked, has 88% CR and 331 acc.

Idk why he only procs his a1 about 60% of the time. 

Assuming you're talking about vs void affin, fully booked you get a 50% chance on his A1. That means you'll, on average, get at least one proc roughly 88% of the time. 

My expectation is simple confirmation bias. I have him only booked for the 10% on his A1, so mine procs 45% of the time, and I can reliably count on at least one proc per turn. Nonetheless, I do always try to make sure I never let it drop below two turns on the debuffs.

Skullcrusher or some other CA champ goes a long way towards making sure the debuffs stick.

make sure y ou have plenty of accuracy as that helps his extension of buffs mine hits heap of them with 290 accuracy on ultra nm cb 

im lucky though im running a slow counter team with skullcrusher which vizier gets extra a1 attempts quite alot

vizier turned my 4 key if i was lucky ultra cb team team into a easy 3 keys ultra 1 key nm cb team, obv team synergy was the key 

altan def aura & dec attack, rhazin a2 dec def & weaken, frozen banshee poison sensitivity & poisons, vizier  extension debuffs and skull crusher counter

im hitting between 29 to 35 mil per key depending on rng