Panthers are quite good on all 3v3 and 4v4 maps. Literally all. Don't know how you play your Coh but from what I've seen and have played against, Panther are used quite effectively at flanking and when they reach critical mass, you just crush everything by going around on the flanks. Nothing will be able to stop it. TDs can't really self spot so that the Panther feeds them vet. Of course, if you only go head on, it's not really a balance issue.
I generally try to avoid using Panthers outside of urban maps because my opponents cover their flanks with mines and AT weapons, so flanking isn't an option unless you are suiciding their arty. And as we both know, frontal engagements with TDs are a bad outcome. More reliable options such as the JP4 cannot be outranged by nondoc TDs and scale better overall.
Okay tell me how you can flank a TD group on Redball in the left or right area, covering the centre as well with AT guns and mines(with all the hedges destroyed of course)? Or Road to Arnhem where the distance between base and frontline is relatively short and mines easily shut down the far side approaches? How do you flank on Lienne Forest when they camp the town and mid? Go try your luck through the forest openings and hope they don't have it mined off and the constant stream of units don't notice you?
Remember, one mine is all it takes to stop your 185 FU Panther flank and they'll be merciless in destroying the crippled thing. One mine.
Key words: Critical Mass. An Allied team that has allowed you to spam 185 FU tanks has virtually lost the match already. Where's the pressure? The early fuel denial? Their early tank power via meds? Are they allowing the Axis team to have KTs/super heavy TDs? Might as well surrender if they have the fuel for this Panther blob o'doom. Hell I might as well get 6 Panthers if they're giving away all that time and resources.
Of course then there's 'General Allies' which is perfect for your flanking scenario and drowns the Axis players in FU, but I'm surprised most 3v3+ Allied players haven't vetoed that place yet.
Note: At no point do I say the TD vs Panther matchup is a bad one overall. It works well enough, though I do agree that the vet II pen increase was too much for TDs in general.