While the main point of a healer is to heal, the way it's designed in FFXIV is so that if you are well geared and know your kit you can DPS as much as you like and heal as little or as required. If not, you'll definitely be spending WAY more time healing. The group doesn't need to be full HP all the time. Most healers also have an "oh crap" ability to get massive healing out in a short time (Assize, Lustrate, etc) or abilities like Lightspeed to make it quicker to heal/DPS.
SCH is basically a green DPS. The fairy does most, if not all, of your direct healing. You give out shields so you can DPS more. Your oGCDs give you instant or AoE heals so you can... you guessed it... DPS more.
WHM's kit is based off of using your lily stacks to build up to a burst DPS. Holy is an AoE stun so your tank can mitigate less and your group can DPS more.
SGE is a shield/DPS healer. You WANT your shield to pop so you can use your DPS to heal the tank.
AST doesn't really have much in the way of DPS options other than a few moves -- but, it's niche is buffing the DPS of other members to make up for it.
I feel like they are mostly balanced. But also, healers shouldn't need big numbers and trying to be outdoing DPS in terms of damage because it's not their role to deal big damage. It's just a nice bonus when they can.
Edit: I can't spell.
