This sucks, too much casting time(which kills it), I believe this one is in maguuma stade(rare skills seems to end up here). You generally better off w/ glyph of lesser energy/energy or energy drain(elite), this skill needs to be worked on to be more vaible.
Glyph of Lesser Energy with the full 10 discount (Costs 5, reduces cost by 15) is about the same as 1 additional pip of energy regeneration.
Energy Tap at 13 energy stealing nets you 8 energy, and works out to be about the same, 1 additional pip of regeneration. With less Inspiration, it has less effect, with more, it's more, of course. Energy Tap is slightly more effective, even with the additional casting time, but the difference is fractional.
The equation used to derive these numbers is;
(Energy gained or saved/[Casting Time+Recharge Time])x3 = pips, which are units equal to 1/3rd energy gain per second.
It's not such a bad skill. I'm just looking for skills that drain or give mana, and for one that isn't elite it's not bad considering it does nothing but steal mana (unlike some other spells that do a whole bunch of other things before you get to the 'mana gain' part).
But it would be handy to have to alternate between this and energy drain