A good combo would be having 1 assassin and 1 duskblade at all times
Having mystic helps with the PVE Buff that adds damage to skills
1 archer to boa and rest is up to you
1 sin
1 duskblade
1 mystic
1 seeker
1 archer
1 cleric
Duskblade+ mystic buffs= damage
Duskblade can use quad on bosses, spam aoes and DT to stop stunning waves and even CC
Sin raw damage and subsea aoe
Archer BOA at all times on sin
Cleric RB or BB depending on what gears and how well your team survives
You might aswell replace the duskblade with a warrior to heaven flame or 1 more stronger AOE but its all up to you
These combos mostly count if you are in squad with bad geared characters
At endgame you might aswell go full seekers/ea/veno and end it with semi-afk...