The generic protonic polaron weapons (meaning not the experimental) has 25% chance on crit proc. Which means, if having 10% crit chance, the chance of the proc per shot is 2.5%, same as other procs. At 20% crit chance its 5%.
Also, its polaron weapon dmg is generic very rare MK XII category, with the generic very-rare MK XII number of mods. Meaning that fleet weapons are better by base dmg/mod wise. This is somewhat compensated if using the Jem'Hadar space set 2 pieces bonus (+polaron weapon dmg), but still lacks behind fleet weapons.
Consequently, to benefit from the protonic polaron weapons requires very high crit chance. IMHO, with crit chance below 20%, the weapon does not worth to be used.
(The experimental version is better, as it has 50% chance on crit, so at 10% crit chance the proc has 5% chance.)