In fairness, that kind of depends on the content.
Dungeons? Absolutely, in 2.0 I actually used to make double WHM parties for the fastest WP grind before we figured out the whole locking mobs out of the boss area with the barrier thing.
Savage and Trials? Not so much, not because we didn't have opportunities to DPS, high tier healers would generally be maintaining dots where possible, but because resources were much scarcer than they are now, and that includes GCDs themselves. Tanks could potentially get wiped out in the span of a couple of GCDs with bad crit luck, MP evaporated if you started spamming much of anything and falling behind was risky because we just didn't have the same kind of ability to catch back up like we do now.
You used to see a lot of standing around canceling casts and hard MP conservation in harder content.