ARC LB: heal?

[Allyrion]

I am talking about my ARC/BRD still in its 30's. It means, is this a skill I can start to trust only on endgame, and all the way from level 1 to 49, is pure garbage?

Pretty much. Best case scenario for Healer LB1 or LB2 while levelling, healer is dead and the boss has very little HP but you all are close to dying as well.
In that case, it would be better to use it on a dps LB but that only applies if the other dps is melee.

You may use it if there are 2 bards in the group, but that doesn't mean it's not garbage.