You know what? I think I can now understand why this would be really over-powered. I really should think before posting

.
Scenario:
8v8
8 ritualists
8x Spirit of Pain
8x Spirit of BloodSong
8x Spirit of Union
etc...
Lets just look at the attacking spirits BloodSong and Pain.
now the highest damage output of these guys I have personally seen is 20 at 15 Communing.
As far as I know, spirit damage ignores armour (for BloodSong at least, this is certain).
16 spirits attacking 1 target will end up dealling 320 damage. Or more accurately, 160 damage + 160 life-stealing. also, forget killing the spirits. With 8 ritualists keeping them alive by spamming Spirit Boon Strike at staggered intervals to deal with the 20 second cool-down (I'm at 10 channeling and I already heal them all for 70hp a piece) they will never go down.
I still hope that Anet decide to increase the party limit to something reasonable like 2 or 3 of each. That would at least stop them from being too overpowered and still allow multiple Ritualist spirits.