We HAD the comet being in par (well, actually better than..) the panther. It. Was. Cancer. It doesn't NEED to be on par with the panther. I panthers are giving you trouble use their counter. It's in the semi tier right before the comet. If the comet is giving the axis trouble and is on par with the panther they...... Call in a super heavy doctrinal unit?
Comet has not right being on par with the panther for the sake of balance.
I mean, the key point there was that it was WAY better than the panther.
The commander upgrade gave a lot more stats than it does now. Emergency warspeed could be used while engine damaged and gave way more bonuses than it does now (though so did combat blitz). The white phosphorous had 80(?) range. The white phosphorous (iirc) could kill models, unlike all other white phosphorous. It had a much higher moving accuracy. It was a crush machine with its insane turn rate, crushing and wiping any squad you forgot to micro for a few seconds. I think it had more rear armor? It had significantly less scatter than it does now. It had 50 range.
At the time, the panther had a slightly higher moving accuracy, much better vet 2 bonuses, slightly more durability (but less reliable durability), was noticeably more expensive, and had pretty busted combat blitz bonuses.
The comet was cancer because it was MUCH better than the panther, not because it was slightly better or on par.