I guess no one have a problem with Sniper J'avo & machine rifle J'avo.
While I agree Sniper J'avo are freaking annoying, they're like Magnum Zombies and they hardly do much damage to even hamper you and I'm pretty sure they're slower than Magnum Zombies in 'prepping' for their next shot.
As for the Machine Gun J'avos I feel it's more on the players fault if you get stun locked by them. They can do terrible damage and like mentioned can stun lock you until they're done with their animation, however they can be very easy to dodge and more likely than not I've walked past them as they're unloading into the direction I've just been in. They're basically the J.Js of this game, they take a few seconds to even fire and when they do they aren't even firing right at you taking them a few seconds to lock on to you and by then you should be either be beside them or out of their line of sight.
Recalling by experience I'm pretty sure they don't even move once they've locked onto your last location unlike Magnum Zombies who usually fire right at you, I've even experienced a MZ who was aiming in front of him and then immediately fired to his right when I was on his right side, RPG J'avos I'm not sure as I haven't memorized their spawn locations, but it seems to be this way too and Sniper J'avo are somewhat the same way with Machine Gun J'avo where once they lock on to your last location they'll only fire on that location.
There is a Ghost in my attic and he says: "It's very dark up here...." ....Oh right....and he also says: "Boo."