From Shaiya Wiki
A few words about team building. I'll try to do my best and write something useful here :)
1. Let's start with the AoE party (Area of Effect). This party should contain a Defender/Guardian to pull mobs and then Taunt, at least one Priest/Oracle to heal the Defender/Guardian and at least one Mage/Pagan to do massive AoE damage. Of course, more Mages/Pagans cause more damage, and more Priests/Oracles can also be useful.
3. 1-15 PvPers: the best party should contain mainly Archers/Hunters and Priests/Oracles cause they can do damage from a long distance. Mages/Pagans also have ranged attacks but because of cast time, the are not the best PvP class. However, their roots and AoE attacks are quite good for PvP. Rangers/Assassins and Fighters/Warriors are close ranged characters but can be successful in stunning or tanking in fox form(Evolution). Defenders are the worst PvP characters because of their low attack rate.
4. 20-30 PvP: Now Rangers/Assassins and Fighters/Warriors lead the list, they are the best characters for PvPing here. Mages/Pagans also became better because of their new instant and AoE skills. Priests/Oracles become weaker than in 1-15 PvP because their only strong skill is the Magic Spot. Althoug this fact, they can still heal! Archers/Hunters are also not so strong here. Defenders/Guardians are also weak here. So the best party should contain mainly Rangers/Assassins, Fighters/Warriors and of course Mages/Pagans (and Priests/Oracles for heal).