And you can totally lose a game in that 1-2 minutes, especially if you're already behind. Buffing it'd be a great way for a better player to steamroll a worse player even more than they already would anyway, without actually making it that useful in an even fight. That said, I think it's kind of meh.
I've never found the incendiary rounds or sturm flamers the least bit frightening at all.
The incendiary rounds just don't do much damage to anything but I guess they at least cover a decent area. Maybe buff the firerate on the barrage to make it saturate an area quicker? I've found that a lot of times the shells will just scatter and miss and I'll just walk around them or pull back without ever even taking damage.
Sturm flamers seem like a weird design decision too since volks already have a flame-related green cover counter that you don't have to give up a minesweeper and repair speed bonus for.
The really nice thing about the rockets is that they are pretty much guaranteed to destroy team weapons fully. Definitely useful if you aren't in a position to destroy/salvage them yourself.
Lieg rounds are a counter pick ability to wipe mortar pits and Soviet FHQ, flamer sturms aren't world-beaters but are there to cover the lack of flame nades after mp40s. They also punish Brits pretty hard that are glued to cover and lack the cqb power.
Rest of the doctrine I would say is great. Just it doesn't have a tiger at the end so struggles to make meta.