I've been using the gamepad exclusively. Up/down for party members and left/right with friendly-filter for FATEs. This approach has saved at least one person's proverbial bacon: during a phase 3 FATE my screen was totally blocked by giant goats but thanks to the left/right targeting mechanism I was able to find and heal everybody. I have enjoyed mouseover macros in past games, but those relying on them should be mentally prepared for that moment when your clicking is obscured by goatbutt.

The ability to choose subtargets and queue spells means you're not losing any efficiency no matter what control scheme you use. With the tank as your main target, you can start casting a heal and immediately begin choosing your next victim patient. As you pick an action for the subtarget, your aim automatically jumps back to the tank. I've done my share of whack-a-mole and this is about the happiest I've ever been spamming Cures.