I agree with you Kordin regarding the EV taking a very short period of time to be repaired. Currently it is up to the defense team to be smart about where the EV is disabled.
IE: If you are defense on Whitechapel and you use an artillery on the EV when it is parked at the front of the Chapel, or when it is starting to come down the hill - this is technically a waste of an artillery (especially because you can shoot it on this map and use the MG in this specific spot).
But if you let the EV get into nice spots on each of the escort maps then you can setup a defense position to be able to have sight of the rear and front of the EV without sacrificing your defensive position.
This is not to say I think the EV speed is fine!
I think the EV is way too slow and I dislike the fact that maps can only be completed as fast as the EV goes - just my 2 cents.