Uhhh.... The Panther's gun is better than the Tiger's out to past 2000m IIRC.
Also, aren't you usually going on about how ranged combat is relatively rare? And a direct hit with an AP shell won't always take tracks off, and rocket salvos are 50/50 at best. Splash from a 122mm isn't going to do what you're imagining.
Also, frontal LOS armor values are pretty close between the Panther and Is 2. At close range, the Panther actually has a pretty large advantage in combat.
AT normal Combat range of 1,000 meters the Tiger and IS-2 can knock each other both out, At Longer ranges the capabilities of both tanks were dependant on the crews and battlefield conditions. The Thicker Front armor of the IS-2 protected it against Tiger I Fire at ranges of over 1500meters while the Tiger was still Vunerable to IS-2 Fire. A Close hit from a HE round from an IS-2 was capable of knocking out tracks or in case of a direct hit dislodge the turret. However the German tank enjoyed markedly better optical equipment than the Soviet tank, a featrue which influenced any long-ranged engagements. The relative Advantages and Disadvantages of both tanks meant that victory in tank combat was most often dictated by teh tactical situation and Crew performance.
So that explains the IS-2 is just as capable as the Tiger, it just depends on the situation - in aces high that means either tank can win.
NOw for the Panther - In overall terms, the IS-2 and Panther were a fairly close match in anti-tank firepower. But the panther carried far many more rounds, 81 against the Stalins 28. The difference was a consequence of the Soviet selection of the 122mm gun, which had larger and heavier ammunition then the German long 75. Both guns had similar anti armor penetration at 1,000 meters (150-160mm) the German projectile weighting at 4.7 kg while the Soviet projectile weighed a staggering 25 kg.
The IS-2 stalin had a significant advantage over the Panther in terms of armour both on the turret front (160mm vs 110m) and Hull front (120mm vs 90mm) the soviet advantage came from the expense of internal volume, another reason the Soviet tank carried so few rounds of ammunition.
Accord to German Tactical instructions a Panther needed to close to 600 meters to guarantee a penetration of an IS-2 while the IS-2 could penetrate the Panther at ranges of 1,000 meters. However both tanks could penetrate each other of a range of 2,000 metres (From the side i forgot to add this). The Panther while a more nimble tank, which top speed was 46 km/h against 37 km/h.
Now onto Range combat, its been my experience over the years of tanking in Aces high, my average combat has been 1000-1400 yards max unless I flank to some hill and shoot down on a battlefield. Of course an AP round wouldn't knock the tracks off, however a close hit from an HE round of the 122mm is enough to knock out a Turret or Tracks. It would have to be a direct hit on the turret ring in order for this to happen, the 152mm were known to do this (KV-2 tank for example simply just had to hit a german early war tank to blow it up).
Does this help answer your questions? I mistakenly guessed the ranges earlier, these numbers have been taken out of IS-2 Heavy Tank 1944-1973