When I was subbed, it would depend on my class.
Warrior: Went prot for CtF type maps and pingponged across the map with Charge> intercept> intervene> heroic leap, but all the others I would just roll arms and roflcopter my way through the enemy to top kbs/damage whether I had a pocket healer or not.
For my shammy I was always Resto and followed the team/fc to support the objectives.
Paladin and druid I also just heal-botted the fc or best geared members.