After doing several BTB matches with my best mate i came to seriously hate plasma grenades. Everyone and their grandma uses plasma grenades combined together with Plasma pistols…
The warthog is a 2 man vehicle and has a much larger skillcap than say the Mantis. To do well with it you need good communication between the gunner and the driver…
I seriously feel cheated when i see people start spamming their plasma grenades. Even the ghost survives 2 direct sticks so why does the warthog explode after 2?
Gun damage on the warthog needs a serious buff, ive loved driving the thing in every halo until now but right now… not too enjoyable 
Plasma pistols can only lock-on from close range so stay a good distance away from your enemies and you won’t have that issue. Same goes for the plasma grenades, the farther you stay away the better and the machine gun is extremely accurate with no kick so you shouldn’t have a problem taking people out from a distance.
I agree that the warthog feels pretty useless in BTB, I think a buff on the damage and health is needed. I would also like to see a bit of a nerf for the mantis. It always takes forever to take down a mantis because they can easily kill vehicles approaching them, trying to approach them on foot is basically suicide. They take a lot more hits than the warthog.
The gun on the warthog seems ok, but it does need more health I believe. The dmr spamming on it and plasma pistols can easily take the thing out. Also the matis is good how it is, with good team coordination (or even by yourself) you can plasma pistol it and bring upon the death-mount!