In PUGs, if we already have two healers, I either go channeler, spirit bomber, SS warrior, or rit lord. If you feel like getting up close and personal with them try the Spirit's Strength build
http://gw.gamewikis.org/wiki/Build:Rt/W_Spirit_Warrior
IMO if you don't feel like doing much and just want to help, Rit Lord is the best way to go. Your spirits have a very far range, so you can sit back (further than the monks) and just keep pressing buttons
But as far as offense goes, I like using the spirits ( pain, bloodsong, shadowsong, ANGUISH) along with painful bond. Some of these spirits are very costly, so I would reccomend keeping them in safety, or carry some sort of e-management skill (AwS or some mes spells will do fine)
Just remember on the offensive, Wanderlust (knocks down), and earthbind ( makes knockdowns 3 seconds) do wonders.