Damn, according to you OKW puma, AEC etc must be impossible to kill with mediums then. Oh wait it's not because they both are paper thin light vehicles
First learn the difference between difficult and impossible and PLS stop putting word in my mouth.
Puma and AEC have sorter range than Scott.
And they are difficult to kill with medium if they do not want engage as the Scott doesn't.
In addition their speed modifier for traveling thru rough terrain are worse so there actual speed is lowered than their stats suggest.
(actually this should be looked since their modifier traveling in road also also too high making the units performance inconsistent as the game progress)