From my point of view Paladin Holy is the best flag carrier.
I might as well have rp walked the flag in
Thinking a bit more, I really think the ideal team would be a Resto Druid/Pally combo.
Early stages of the match: Druid to run it across the field, and then hand it off to the Pally so the Druid can run back and help get our flag back. Late stages of the match: Pally escorts Druid and if (odds are there will be) heavy resistance is foreseen, Pally takes flag and druid heals/CC's.