To be honest if we exclude the Master's Psykers (which were the most powerful psykers in Fallout lore) most of the remaining ones are really weak, most powers only include visions, "communicate" with small animals ( and usually only one type of animal: rats, radroaches, giant ants), and use telepathy to communicate (through dreams or amplified using some kind of tech).
And usually some of these have already bad side-effects (need medicine to not go crazy, need drugs to fuel the psyker powers, needs special mental blocking devices so it won't be painful, etc).
So I don't see a big chance of making psykers overpowered, of course if we go the Master's Psykers route they will be overpowered if not in check.
Oops I didn't see Hassknecht post in time while I was posting mine...