OP, you have to keep in mind that you're draining the targets health. You're likely seeing that 44 number because you're hitting a lvl 1 training dummy with it, and you can't drain it of more than its max HP.
To your addendum, while your actual gear doesn't matter in PotD, your damage does scale based on your PotD weapon level.

Hitting a lvl 60 training dummy, as a lvl 65 RDM in i270 gear, Drain is hitting for around 1090-1150 and healing me for exactly the same amount. It's not a super amazing ability, but it's not as completely useless as you make it sound.