This is something most casters didn't have to do for a while (or at least it wasn't very viable) but I've learned in the past months the sacred art (used mostly by melee, esp rogues) of "Weapon Swapping." (cue Angelic singing)

See, most healers think you need to make a choice between the 2, but guess what? You don't! >:D

Keep 2 caster weapons on you, one with Heartsong, the other with Power Torrent, and you can switch them during fights to get whichever proc is off it's internal CD. I personally have heartsong on an ilvl346 spirit weapon (which I have equipped for the majority of fights), and PT on an ilvl 359 pvp weapon (most SP on it, matching throughput with more throughput). The nice thing about this way of healing is you can very quickly adjust from throughput to regen with ease, match your weapons (if they be 1-handers) with appropriate off-hands and the customization gets that much better.

Here's the kicker though.... lean in close, as Blizz might not be aware of it, and it might still be a secret....closer....closer......... the procs are not exclusive to each other! I.E. Heartsong and Power Torrent STACK with each other!!! You don't even have to choose between the 2, you can have both at the same time!!!!