SU-100 it is almost a complete analog of JagdPanter. They have similar guns, similar armor. But in the game, the SU-100 is a little better than the SU-85. Su-100 needs three shots to destroy a half-track mortar. I think the SU-100 should be like a JagdPanter - good armor, good damage one on the battlefield.
The SU 100 is nowhere near comparable to a Jagdpanther perfomance wise. The Jagdpanther uses a Pak43 cannon, same as a King Tiger, and pretty much the strongest tank gun in the war. It had extremely high penetration values and an unparalleled accuracy because of skilled crews and viewfinders/radio communication.
The SU 100 lacks almost everything of that. The D10T has a higher caliber, which actually makes the weapon penetration worse, because a 100mm needs more acceleration to get to the same speed as a 88mm shell. this is because most of the time the larger shell is heavier. There are more factors, but still - the Pak 43 was much better against armoured targets.
The armour IS pretty good, it also has a good chunk of hitpoints for its price, and the armour is decent against axis AT guns, Panzer III/IV, and with veterancy also withstands Panther shots.
Compared to other allied tanks the SU 100 is a pretty easy to mass assault gun that can deal a lot of damage against even the heavier axis tanks like Tiger, Panther and even the King Tiger. Which is no other allied tank able to (except for shoot and scoot with Sherman Firefly or using Pershing/IS2).
One thing I'd consider would be to put the damage higher - right now it deals 137.5 damage, just like he Panther/Tiger I guns. However, this has to be carefully tested because it's pretty easy to get multiple SU 100. For 2 Panthers you can get 3 SU 100, which will give them a hard time.