- First, he is not "hard to hit" and
more durable. The only thing that makes him more durable is the "hard to hit".
- Then, he is arguably not more mobile. The ability to move backwards counts as mobility. He is a super fast garbage truck that moves super predictably.
- Then, some people consider the unreliable 1d6 missiles and the tiny TLSR/SC not to be worth a DL/dissie.
The only point for taking a Ravager isn't the idea to charge with it. With the FAQ, you can, for example, not want to have half your army as an airborn force that will make you lose the game when the other half of your army is dead.
Charging with a ravager clearly isn't about damage, since he got 3 attacks only. He should be far from assault, so i wouldn't plan to use him to soak overwatch. But if a unit of scions deepstrikes near, charging them to make them shoot you once on 6+, then not shoot at all, is a perfectly fine plan