This actually seems intended to me.
Another normalization of flame damage across the board, all behicle flamers deal the same damage, all leave the same dot, doesn't matter if its WASP or churchill croc, they have exactly the same killing potential.
I noticed though, that the KV8s flame jet time is like 3 seconds longer than the Hetzers and the Churchills. Didn't check the Halftrack and the Wasp yet.
Edit: Also I don't know if that directly effects the DPS.