Exposed, easily hit and extremely limited movement options. All factors which considerably reduces the life expectancy of a tank driver and crew. The latter being key for a Magrider to avoid death. I would also argue that due to the limited use the Magfart this ability has been reduced quite a bit already. Harassers are the true kings (and actually a potent threat) in these situations. Basically, when this happens it is because the entire base is so safe to navigate the base has already fallen to spawn camping (and it is probably going to be stuck there...).