wasting mana by not letting consecrate tick?
I've never given it a moment's thought to be honest. It ticks away quite happily while it's on cooldown

I just kind of accept that I'm going to have some downtime after every pull, which doesn't work out too bad given that I'm usually waiting for overland mobs to respawn anyway.

You've obviously made up your mind here, but if I were two boxing now with an eye on going further later on, I'd probably go with two mages for the point-blank AoE power. Healing just isn't an issue until you start hitting instances / doing Outland group quests in any case.