I noticed you have over 2600 games as soviets. At this stage tips don't really help that much, the only thing that might help is to play 20-30 games as okw and lose hard sometimes against soviets.
So it seems that all vehicle flame weapons were affected by the DOT damage nerf. Hmm, well, this is definately unintended, i hope relic will fix this soon.
Probably won't.
Working as intended, read the patch notes
We are increasing the time per tick for damage over time. This will include all incendiary abilities, Molotov’s, and flamer dots that vehicles leave behind.