Let's not get into the standard misunderstanding.

When we say healers should dps in dungeons, no one (sensible) means you should somehow manage to keep a paper tank and 3 aoe-addict dragoons alive while simultaneously topping the meters. If your tank is demanding every GCD just to keep them alive then by all means pour heals into them. That's fine.

What they mean is if the party isn't taking massive damage and you have spaces of free time, even if only 3 seconds in-between your heals, you make it your goal to add some dps there. It's fine if you find it difficult at first as long as you're learning and on the lookout for opportunities. Both SCH and AST can weave oGcD's with their aoe too and WHM's stuns trash packs and you can weave with Misery. You become a better and more efficient healer for it.