@OP, BLUF: Flamewave is gd awesome in the right hands and is already entirely different from Drake Gun in terms of both potency and mobility. They’re apples/oranges to one another. Trying to say they’re the same is like calling two totally different guns equal because they both shoot bullets.
Value depends on the class Flamewave’s being used on and what the group needs in order to be rounded out. I run it on BW and it’s extremely effective. Being able to do full-duration blasts with near-instant charge time for next to no overheat is potent af, combined with the facts that you can go balls out stacking power and that you’re always in range for World Aflame.
It’s especially valuable on BW because it’s also the only staff you can spam basically 100% of the time, even without a Heat Sink build, without ever having Overheat issues. BW has heat issues with other staves whereas both Pyro and Unchained can manage any staff with ease in terms of heat control. Similarly, Flamewave kinda sucks on Pyro/Unchained because they have to eat the full-duration charge time, which makes it a lot clunkier than it is on BW. This is especially true when you factor in the weapon deals no extra damage on crit and doesn’t generate enough heat to make Heat Sink worthwhile (so rip Flamewave Pyro), you lose a 25% power multiplier on Pyro/Unchained and an additional 10% modifier while on Unchained, and you sacrifice BW’s mobility (rip Pyro/Unchained). Basically it’s garbage-tier on Pyro/Unchained and god-tier on BW.
As far as obstructing the line of sight goes, I agree in general but it’s typically only an issue when people don’t know how to use the staff and you can’t trust them to keep you safe while you’re wading into a horde you can’t see. Critical to have the spot key assigned to something you can spam while firing and also to be cognizant of how much you’re blocking ppls’ views. Flamewave users can almost always fire into the meat of a horde while leaving 5-10ft of breathing room for melee to engage unmolested by fire. The biggest mistake I see ppl make though is using it exclusively defensively (this is often a side effect of ppl using it on Pyro/Unchained due to the aforementioned charge time and the fact it will take them twice as long to kill things with it compared to BW).
Edit: Final note on potency - BW Flamewave consistently has up to ~250% power thanks to Pyromatic Surge (10%) x Barrage (25%) x Power vs (up to 20%) x Power vs (up to 20%) x World Aflame (up to 25% but pretty much always maxed out in combat when it matters). It is extremely devastating and I’m convinced BW/Flamewave were made for each other, with even the class-specific portraits alluding to it.