3 minutes, still imba trinket!

Actually, it's much better than Mindtap, especially on short-duration fights, like Kazzak or Vael (...not that it really matters with Vael).
In a 10-minute fight (4 uses) it's about 27mana/5 (3200 mana total), provided you use it once as soon as you're down 500 mana (which should only take maybe 10 seconds) and as soon as the CD is up each time after that. Even if you use it only three times, it's still 22 or 23mana/5 in a 10-minute fight. Hardly comparable to Mindtap, or even SotS. At 20 minutes it's down to 17.5mana/5 (6 uses), but at just after 21 (depending on when you first use it) it's back up to 24mana/5. [Because of the CD, the closer the fight ends to just after a number of minutes divisible by 3, the more mana/5 it equivelates to].
(lotsa numkbers, sorry, I tend to get carried away...)

I think it's accurate to say this far outshines Mindtap, and still average 4 to 6mana/5 more than SotS on average.

lol wrong... its from 4 Horseman chest (when you beat the encounter)