About it's power, it's not sub-rate. The LB doesn't work like a normal skill, based on your personal stats.
A LB from a bard is as good a heal as an LB from a healer.

That said, healing LB is usually only used for LB3 (the mass raise, as viridiana mentioned).
I've seen it save some wipes and usually it's when the bard uses it.
The LB1 and LB2 are underwhelming even for healers, when LB2 heals for about as much as a Cure III (longer cast time, but of course it's free).
A cast time heal can never really be that good in this game when people are topped off so easily.
It'd be better as either instant (emergency) or a Heal over Time spell (stability), to really justify using it over a dps LB.