the jackson is another story... even now i wonder why the devs decided to put the faction with the most kickass earlygame infantry with the strongest lategame tank destroyer....
It wasnt like this originally, I belive jackson was ment to be used as a flanking TD and fast TD, with decent penetration, but design didnt work because behemoths like elephant\KT\JT when didnt care about much about that and pretty much when supported they were unkillable.
Point is being that all other TDs lack the turret or in case of FireFly have poor ROF, Jackson retain all of the advantages it had (range and mobility) while got proper penetration of other TDs.