The thing about healer LBs, they don't refill as nearly as fast as a DPS LB when they can score a kill or more from it.

I'm not sure what the formula is for the healer LBs filling, but rarely do I ever see it fill more than once per match( I tend to be very picky when I pop it, so I usually don't use it more than once a match). Some matches I won't even have a need to use it because-

1) Most of the party isn't even in range of me to be targeted.
2) Our team decides to play super-conservative (hide @ 2 tomeliths whilst one team kill-farms the other) when I do have it.