I actually think the flamer on the hetzer is fine. It's the Kv-8 and croc over performing.
It's true that croc is an ultimate machine of doom for infantry but it also comes very late, at the same time as its hardcounters, JT and Ele, so it has in fact no window of opportunity. At the same time its light counters: stug and JP4, are both available much earlier and for fraction of the price they are worth. People just have to learn to expect the croc and not rely on infantry based AT to much unless they are sure there is no croc coming from brit player, especially in 1v1.
As for KV-8 it was really OP in some patches, but right now it feels ok imo. Thanks to its unique flamethrower damage profile, it is more a tool to make enemy squads retreat than a wiping machine, if you don't let it attack you at HQ, it most likely is not going to kill any model that has full health. The dot damage simply means it is not that good at chasing retreating squads.
And here is my only concern about giving hetzer the kv-8 flamer - the hetzer has quite good top mg, that seems to be really good for chasing squads. If it got the kv-8 flamer, it should probably loose the ability to shoot that mg. Maybe it would be good idea to give it option to either upgrade to top mg or to better flamer.
At the same time it would be also usefull to think about hetzer vet. Its something that we don't look seriously at, becouse its hard to even get to vet1 with it, but it has 5 stars of really powerfull vet, including flamer buffs. This should probably be changed, mostly into defencive buffs.