I honestly can't see why crit-build is good. Seriously, I'm first Crit Lover in 100 mile radius, but in Underrail, especially psionics should sacrifice too much for this.
I still can get decent critrate with Elecrtokinesis and Psychostatic Electricity like 25% crit.
What you crit score without using rare drugs that only available in second half of the game?
I tried playing Tranquility after Psychosis(virgin run even!) and I felt like an impotent, castrated manlet.
Psionic Mania is what makes is it valuable, since you usually only need one crit to instagib enemies, and it being reliable, it allows you to plan tactically. If you craft your gear you can get ridiculous bonuses on critical damage, making one crit worth more than >3 (more with Trance) non-crits. Even outside of the guaranteed one, the difference between 1/3 and 1/2 of your spells being criticals is very noticeable in sustained engagements. You have to pop psi boosters like an addict tho, usually already on the first round so the CD starts ticking.
I never took Psychostatic Electricity on pure PSI since stuff dies before you can stack it, might be interesting on a hybrid.