The Banshee was perfect in Halo 3, if you ask me. It had both of its weapons that did a good amount of damange, had decent survivability, but wasn’t a tank either. I think the most important aspect regarding its survivability that was messed up in Reach and Halo 4 is the fact that it could not be killed by Sniper Rifles. You really had to use anti-vehicle weapons to take it out, as it should be. The Banshee was balanced by the fact that you couldn’t look down more than 45 degres, meaning that it had to be used for strafing runs rather than area control. If you missed a guy with your Fuel Rod Cannon, you had to fly out a bit, turn around, then take another go at it. In Reach and Halo 4, you can just turn on the spot, look down, and shoot at him right away again. Its flips were sort of slow, meaning that you couldn’t dodge every single shot fired at you. You could evade targeted missiles and whatnot, but regular anti-vehicle weapons could still get you.
You had to be smart with the Banshee in order to use it well, basically. It was balanced, fun, and a great asset.
In Halo 4, the Banshee was a mess. It was fast, it was overly powerful, and while it had low health, it still killed a ton of stuff before it died. It removed every weakness of Halo 3’s Banshee, and then buffed all of its strengths. If the enemy team had both Banshees, your team almost automatically lost. Getting 20, 30, or even 40 kills in a Banshee without dying happened far more often than it should have. Yes, you would sometimes get games where you’d fly away in your Banshee, get 2-3 kills, then die. But compared to the former, this was a rare occurrence. Oh, did I mention homing Fuel Rod Cannon shots onto vehicles? And sure, perhaps it could be taken out by the Sniper Rifle, but that just seems like a poor attempt at balancing this overpowered death machine. As much as I enjoyed going around getting Rampages in the Reach Banshee, it was definitely overpowered and should never return.
In Halo 4, the Banshee took away all the strengths of Reach’s Banshee, but built onto it’s weaknesses. You can’t zoom around like a madman anymore and get several dozen kills in a game. But now the, if you get 5 kills with the Banshee without dying, I’d consider you to be a very lucky/skilled player. This this is a flying death trap, really. It will die by being poked, really. If you’re flying and accidentally nick a wall you lose half of your wings and you’re now on fire. It doesn’t help that everybody can spawn with a Plasma Pistol and knock you out of the sky at any moment. This thing is too fragile despite having the weapons be nicely balanced. The only map on which I’ve seen the Banshee be effective is on Daybreak, but that’s because there’s so much cover up in the air for the Banshee to run and hide behind that it can easily pop out of the battle at any time. An air vehicle should not have to rely on cover to be effective.
The Halo 2 Banshee was nice and balanced as well, but the lack of Fuel Rod Cannon in multiplayer might annoy some players. In this game the Banshee is basically a flying Ghost, which is not a bad thing at all. I enjoyed it, and would not mind it returning.
Lastly, we have the Halo 1 Banshee, seen in multiplayer on Halo PC/Custom Edition. It was fairly balanced as well in its own right, but it’s hard to compare to the other versions due to a lack of destroyable vehicles. It had both weapons like all but the Halo 2 version, though it had no boost and could not do flips. Not a contender to return in its own right.
In short, the Halo 3 Banshee was the best, the Halo Reach Banshee was overly good, the Halo 4 Banshee is a flying death trap, and the Halo 2 Banshee would be a good version to return as well.