Whether or not to sack a low psi soldier is up to you as the commander. Much depends on to what degree OpenXCom replicates the original game when it comes to psionics. I am still playing my first game so I really can't say what a "safe" psionic strength is.
I have played this game since 1994 and the original AI "cheated", in my opinion. If the aliens could see just one soldier, ALL of the others were also at risk. Also, after turn 20, the AI knew where all of your soldiers were - and then the "psi-puppets" came out to play.
Much also depends on the game difficulty because the psionic strength of the aliens increases as the game difficulty increases. A soldier that is reasonably safe at a lower game difficulty may be alien psionic fodder at higher levels.
I guess I'm a heartless and PARANOID commander. In general I do not employ soldiers with a psi strength lower than 50, increasing this to 60+ if playing on higher difficulties. That low psi soldier with high reactions and firing accuracy is a prime candidate to effectively shoot all of his/her teammates in the back.
As for assigning them to base duty, why pay them to sit on their butts? What if that base is attacked? That low psi soldier can just as easily kill many in the base as they can when assaulting a landed UFO.
Only assigning them for missions with no psi capable aliens depends greatly on having a Hyper-wave Decoder. Scouts are the exception. They do not have psi capable aliens until the Ethereals show up.
Lastly, in my opinion, if you can afford it, sack the "psi-puppet" soldiers and get ones with "nerves of steel." If you can't afford it, you may be stuck with a great potential liability until you can.
Remember, in XCom, Murpy is the undisputed "Lord and Emperor!" and sneers at those who fail to understand his law.