I've narrowed it down to Warden and Druid. Both I'd be playing as full on support / heals. I don't have much experience in Hib, so I don't know what will be needed. Seems like Wardens are a bit underplayed here.
Bunch of druids on hib. Warden might be a good choice for solo potential when no groups are available. What helps me is having a few different toons rolled up to fill different spots depending on the circumstances.
It sounds like you are trying to be pure support, so I'd say Druid for sure. Much more sought after in RvR/PvE and just a stronger class overall in a group setting. If you are going small-man, then it will depend on your group composition. If you want the ability to melee some to go along with heals/pbt or maybe you just don't have anyone in your group that wants to play a Bard (for speed), then go Warden. If you just want to purely heal like it seems like you are suggesting, then again - Druid would be the choice.
Assuming that no major changes are made to the present XP system it should be fairly easy to level both the Druid and the Warden in a reasonable amount of time.