Jackson still has crush.
Jackson turret rotation is quickest of all TD's;
Jackson speed is best of all other TD's; it can kite too well.
Jackson range is more or less the same as firelfy.
What does the ISU have in comparison?
The rest have unique abilities at least...
Running an 480 HP TD into infantry will likely not end well.
Turret is one of it's few saving graces, it doesn't help as flanking with a M36 will often end up with a very dead vehicle crew, due to its low HP.
Kiting is it's only mean of survival due to low HP and poor Armor.
While range is good, in many maps and situations you won't be able to use it to your advantage due to shot blockers or requiring a unit to spot for you, which will mean more bleed in the lategame for USF.
The ISU-152 has a completely different role, not sure why you bring that unit up, it could use some buffs but it's not a TD.