Wow, first off, if you are doing very good in PVP (expert and above) and PVE (clearing above Unity 30), I think to it is BEST to specialized in one path and MLB.
I will break down you question one-by-one, but assuming you are doing VERY GOOD in above statement.
1. You should LB your Cybella GS to lv38.
2a. You should LB your Kane GS to lv34. || 2b. You should LB once your Kane GS, but train one Kane GR, because I see you don't have Trigger-Stun in your team, yet.
3. With Vincent berserker lv40, Kai ninja (can break to lv40), Shizu ass and Darrion BK. I think this squad is good enough.
Side note, you asked about 3 archer, if you don't mind free win for others in PVP.
a 3 or even 4 trigger-ranger team is a dream, a very fantastic dream! Once it triggered, you will see the magic!
Many thanks for the answer. I personally don't like GR because of knock back. However, thanks for the idea and I appreciate about 4 trigger-ranger team, haha. May b I will keep another hera Cybella for GR and do that dream team. For now, I think I will go for Kane SS first because I feel waste if use ares Kane for fodder (hope will get more Kane in the future). And will reconsider 4 ranger team, it should be really fun.