Having a T34-85 is a big bonus though. It's probably the best doctrinal medium tank, given it's performance/price. Not only that, but it can be used in the same way the Panthers can, in teamgame lategame: Hail Mary push. You could do it with a Comet, but given it's price and AI power, you won't get far. Sure it will bounce a few more shots than the T34-85 but still...
That's one massive argument in favor of ISU if you ask me. Of course, your arguments concerning KV2 chunkiness and the fact that it comes with another AI heavy tank, the KV8, renders the commander generally unfavorable.
imo 85s is a weird one, since there is not whole a lot of difference in firepower compared to 76s. But they are better at roaming doing very deadly counter attacks. Still 2x 85 ~= 3x 76s. Lately I started to like 76s a lot. Cheap, low pop cap and enough firepower for sharp maneuvers. It is also the best "trading" tank, hence the ram ability.
In terms of comparing to comets, the brit tank is just better. In terms of AI ,they are inferior, but they have "bliz" lots of penetration to brawl with heavier targets and phosphorous rounds to shut down AT. They also wipe the flor with P4s.
On topic my thesis is that ISU is much more effective in team games. I guess KV2 can be useful, if you are not tryharding and want to have fun. Although you can still pick Windustry, skip KV2 all together and be effective. KV8 covered by Su85 and some mainline is extremely deadly, especially vs A-moving Ober guys. Get the repair stations and steadily bleed the opponent.
For the other commander I had a nick name in Russian "Cыч" (sort of like a local type of Owl), because you build a nest in some building early game and just troll the Axis. Back in the days used to be able to do on both VPs on Redball. Good luck dealing with that without Firestorm Fun times.