15% damage increase per target hit.
Duration longer than build up
Recharge longer than build up
I can get shadow maul ticking 8 lots of 65 damage or so with a full drain, at level 50.
For AV's Build up would be better, because as the fight goes on there's no one around to drain anymore and you only get a 15% boost compared to the other scrappers getting 100% but most of the time I prefer soul drain.
"Well, they found my diary today.
They were appropriately appalled
at the discovery of the eight victims
They're now putting it all together.
Women wrapped in silk
with one leg missing
Eight legs, one body, silk,
spider, brilliant!"
it was a kinda let down to me BUT
i was doing legendary find the first 25 lvls, i dont think i wil even use it much!
HeHe, I find it crappy at the moment but Cynic has conviced me with the 15% buff per target 
and works great in teams.
You saw me use it right? 
I love to TT them first then possition for a good old self buffing before firing off my attack chain
"Well, they found my diary today.
They were appropriately appalled
at the discovery of the eight victims
They're now putting it all together.
Women wrapped in silk
with one leg missing
Eight legs, one body, silk,
spider, brilliant!"
Souldrain hits just as much at lvl 26 as it does at lvl 50..just time it right..
Soul Drain is a very useful power but IMHO is more useful in teams than solo, so it can be partially dependant on your playstyle. I use it a lot on teams as an opening attack on groups of bad guys and love it. Solo, the groups of bad guys are generally smaller so it has less use, not entirely useless though because a gang of three or more can give a nice boost. As solo play tends to be at your own pace, then you are less often required to have huge attacks with smaller groups of villains and the chance to rest/regen when needed and hence less need for a massive boost to attacks. Thats my opinion anyway, I find I use it less solo than in teams. It's always nice to be able to hit harder though... any time.
"Pride is all well and good but a sausage is a sausage"
For Lent I gave up...
Hope
Just got "soul drain" on my DM/regen this mornin infact
just wondering how good does it get
it only seems to effect 3-4 targets atm even with like 3 yellows popped
does it get better? how good does ur damage get
also
with 3 recharge how good is the recharge? like build up?
never played DM :P