As a healer I have no problem with, and even like, big pulls. It's so boring to toss one heal off, afk for 30 seconds until another heal is needed.
That being said I've been in some groups where the DPS just DO NOT know what to do. I was in a party with two BLM's and they single-targeted like they were gunning down the last 3 percent in a boss battle. A pull with 15ish mobs literally took about 5 minutes to kill down one by one. Tank and I were /really/ confused at the DPS not AoEing, and they didn't really respond as to why they weren't. It was weird.