If you're asking whether the stun effect should last longer than a few seconds, then I would say yes, always.
Yeah, it is what i was thinking when replying. I dont know exactly how long the stun last as now but from in game experience i think it is very short. I presume that short stun duration is a trade off for hight dmg of the 2 rockets, if both hit but if i'm not wrong, fire rocket slow down the already slow rof of the tank so a bit too much of a trade off. Get both rocket to hit is difficult, tho.
If stun effect can be longer, it will help with firefly's slow rof, allow another shoot may be.