This does however, not really have anything to do with you not enchanting Power Torrent. You could do the same thing if you had Power Torrent.
Also, you said you had almost 3300 spirit - that should be more than enough, even without Heartsong. Also, from what I remember, Heartsong only equals about 108 spirit, while Power Torrent gives you an average of 120 int, which should be superior. Also INT does increase your mana regen, although not as much as Spirit does.
And don't forget that it's pointless to have fights ending with you still having mana, that would just be a sign of excessive regen, that could instead have been put into throughput, which overall also removes a little strain from other healers, which could in turn, mean that overall, your whole raids mana in total increases.
Also, wouldn't it be better if your resto druid used his innervate on someone other than himself? The way it is currently, he would regen more mana overall (if he has the right glyph) if he used innervate that way.
I obviously don't want to force you to do something you don't want, but I think it isn't wrong to show you what you could improve