There's only a small 8m range between the bazooka's medium range, and the Flammen's
maximum range, and some of that is even taken up by the HT itself (since the HT's cab/engine block will be closer to the Zooks than the actual flamethrower). Keeping a HT within the bazooka's Long range is difficult (near impossible if you're microing multiple HTs), and means that you can't circle around ATGs.
So in practice, your HTs will be operating in a Bazooka's Med/Short range, which means that they're faster firing and more accurate than you give then credit for.
You also fail to take into account doctrine buffs like Steady Sights or Tank Reapers, as well as Officer buffs or even vet.
They don't have to be a suicide unit.
They are.