From commando point of view - 4 sec is more than enough. Still you have more than enough time to place 4-5 shots. Nuisance, not a nerf.
Gunner got buffed. Burn-thingy was good, slow is awesome. Not only you can see anyone caught in the blast - now you can catch them. Team-wise gunner got buffed immensely, shareable shield, and slow helps team a lot more than burn.
Somehow it feels much better to keg+bazooka a crowd and then rush with leg in between then running like crazy and laughing maniacally(optional, but recommended).