21 Blast or Stun Mastery

Drain seems very useable at level 1

Drain's usefulness increases exponentially as you level it up. It's not just that it heals more per cast, it's that it can keep up better, so you need to use it less. By the time I'd maxed it, I could use several blasts and 1 or 2 drains then go on to blast several more times. At level 1 drain if I tried that at Himes, even spamming drain wouldn't keep up.