Not that I have any solid advice, but I recently stumbled upon this thread on their forum that I've been saving so that I could go over it later:

https://forums.aiononline.com/topic/...class-to-play/

More resources:

http://aion.mouseclic.com/wiki
https://aionpowerbook.com/powerbook/Main_Page

Also, in Aion, party size is six.