Key is knowing when to use what and anticipating damage. Casting a heal so it lands just as damage is taken will help in many ways.
You should use a HR rotation when you have a throughput CD up (wings, Shards of Nothing, hero, etc) and the raid is taking enormous damage (see: earthquakes on Tectus). It's very good to burst up stacked groups when you have a throughput CD, but is otherwise lackluster due to the mana cost. If the raid is spread, abandon it altogether.
Much better to regularly single target raid heal with HL, FoL, HS and EF (or WoG) so you're keeping consistent heals on
