You have to remember that this power is a regen/recovery power, not a direct heal to either bar (like Stygian Circle). It works great, the more enemies you have. I've been able to cap my regen and recovery on my Dom easily by jumping in the middle of a group. This power is what saves my Dom's tail every time by helping me recover from the alpha strike.
It's best used at the beginning of a mob instead of at the end when you think you might need it. It will keep your health and stamina high rather than make it go from 0% to 100% quickly, although it will do the latter eventually.
@Nurse Donna
You can find me on Infinity, Exalted, Liberty and sometimes on Virtue or Freedom
There is a steep, steep learning curve on how to use Drain Psyche without it being essentially a suicide maneuver. To get its max potential, you'd think jumping into that full spawn group before the rest of the team scatters it would be the thing to do. However, unless you've got really good +def set bonuses or used at least a medium purple equivalent inps, you'll be dead before you can take your first shot. I have come to the conclusion that I can't think of Drain Psyche as a survivability too. I have 2+ equivalent heal IOs slotted in my Drain Psyche and the +regen really isn't that noticeable. On the other hand, the slotted 2+ equivalent end mod IOs are noticeable, but I still can't go all out as if I had Speed Boost on me. Still it is good to have when you're working over an AV or something. Speaking of which, Drain Psyche's -regen is good for AVs especially for those times where no one else on the team has any -regen debuffs.
The bottom line is that, yes, I do and will continue to pick up Drain Psyche in my builds.
Edit: in response to NurseDonna's post
Dominators have ways to disable an entire spawn group before jumping it. It's a bit dicier with a Blaster.
Teams are the number one killer of soloists.
Thank you everyone for your helpful suggestions. I can't afford the expensive io's at this time, so I'm gonna make some regular io's from the university. Slotting suggestions? 2 recharge, 2 acc's, and two end mod's? Thanks again everyone. You guys rock! 
Drain Psyche is awesome on my fire/mm. The awesomeness is not so much for the HP regen, but just using it on one mob for recovery is pretty nice- particularly useful when fighting clocks, freaks, maltas or any of the other -end recovery npcs.
Still, when you jump into a mob of 8 or so npcs and use Pyschic Shockwave to disorient them, then Drain Psyche to boost your regen/recovery, you can pretty much have a blast using whatever your primary is.
"Most people that have no idea what they are doing have no idea that they don't know what they are doing." - John Cleese
@Ukase
Thank you for that response Time to play!
My water/mental blaster is currently lvl 38 (thanks to double xp weekend lol) I picked up drain psyche along the way, but it wasn't useful to me. I was expecting to see my life meter and end meter boost up like my warshade. What are your thoughts about this? Thank you.