It's for sure Druids. They don't need to line up perfectly but not having to dismount and remount is a huge timesaver when you figure just how many times you are mounting.
The biggest issue though with the flight form is making sure you are touching the ground. So setting a hotkey to go down before attempting to gather is the best.
Another reason why the flight form is huge is you can completely ignore mobs/combat, Going over a node that has a mob on it, you can herb and then just fly away. Even if 1 of your group misses the herb you can just keep going on without a loss in time.