And besides, the mass driver is probably the weakest weapon in the human arsenal 
Sarcasm?
Half truth and half lie ( so half sarcarsm I guess ). The mass driver is the weakest weapon in damage per second. It does one shot per second at 36 damage. The rifle deals more damage than that.
So, when fighting against a Tyrant, I'd better be using a rifle than a MD. First because I'll probably cause more damage to the tyrant with the rifle, and second because I'll probably die and lose far far less money that way

MD is very weak and it's only 2 good features are it's perfect aim and it's ability to kill a dretch instantly and a basilisk in one second.