My thoughts exactly. The Halo 3 Laser felt perfect, it just needed one less shot which it has now. I miss those Laser fights on Standoff/Valhalla/etc... I think one of the reasons why people hated the Laser (subconsciously at least) so much in Halo 3 is because there were no weapons to ping it long range. The BR was too inconsistent to truly pesk/kill a Laser kill from any sort of distance, but now we have the DMR so we're set.
I always think nerf only when it's needed and buff the weaker areas of the game. Glad to see this is a pretty apparent theme in Halo 4 (for the most part).
Not sure about pinging it mattered, i use the laser almost always with the scope. Of course quite many people do "flinch" when shot.
Nerfing tends to be far easier often, as i've understood it, easier to control its effects.
I think even had the laser given a proper warning to the vehicle being targeted, it would still be insufficient. Between the scope on the laser, the large kill zone and the relative lack of maneuverability on the Warthog to evade the shot, a couple seconds warning wouldn't have let drivers make effective evasive maneuvers. The Missile Pod gave drivers a warning when it was just pointed at them, which combined with the slow missile speed and wide turning radius of the missiles, made it more fair. On maps with short sight lines or around blind corners you could just mow guys down point blank with the missile pod/rockets/power drain/etc. anyways.
I'd probably modify, err, nerf the laser more than just remove one shot. I'd also remove the scope (to me it felt pretty useless anyway, unless shooting infantry), add slightly more charge-up time... and give a warning sound to players being targeted (would be relatively easy to conceal by aiming elsewhere but would still help detecting the laser).
These in addition to keeping laser in maps with shorter line of sights, urban maps for example (and obviously i'd avoid other anti-vehicle weapons and gadgets in short LOS maps, except maybe the plasma pistol).
EDIT eh, found a hole in my suggestion to keep the weapon only in short LOS maps, those have far more hiding and ambush spots. Hmm...
I do think the laser worked more or less fine in Halo 3 BTB, the maps and the weapon just needed tweaks. At least i had a lot of fun in Halo 3's BTB so i think it was succesful overall.
Oh and i gotta note a weapon my friend suggested for Halo, a rocket launcher with extremly fast unguided rocket with very low splash damage, mostly useful against vehicles but unlike laser it wouldn't be instantly hitting.
Obviously just a concept, personally i don't think it is needed really though if Laser-like weapon is needed, it could fit the bill.
Also, Fuel Rod Gun should have been replaced by the Plasma Launcher (for Halo 4).