good observation and i believe that the rocket hog is on the one that has the big building in the middle and has the wraith. And the gauss hog can shoot from VERY far away so it could take out the mantis from a distance but if it got close it would be even.
1. You forgot about the rocket warthog.
2. The gauss Hog destroys the mantis.
3.A plasma pistol makes using a mantis a challeng and people know what maps the mantis is onso they just use their plasma pistol loadout .
I love the mantis but when you use it you have to be careful.
I love fallout its not as good as skyrim but its good. It needs better graphics though hopefully they nail the graphics in Fallout 4, ive never played 3 im gonna play it soon but i liked new vegas i still have to beat that also.
i think it just might work if u make indestructible vehicles and all you would have to do is save the game type and play it in custom games i love the idea and i just might do it.