I have lost many, many games due to a good charger being on the Bad Guys and shutting us down totally, especially on the Rig where they can pick you off as you come down from your spawn area, even.
As for the laser, it is there for two reasons:
1) So that, in a third person shooter without aim assist, you can tell where you are shooting more easily than relying on the reticle which barely gives you any information about depth.
2) To balance out the Charger's power. All Chargers are one-hit-splat at full charge no matter where you hit the target (snipers in other games need headshots for that, usually). Without that laser, it would be way too difficult to counter something that is really, really strong, like if Bowser suddenly turned invisible and teleported around during his forward smash.
It does add the fun psychological effect to the Charger, as well, because dodging that laser is much more fun than dodging invisible death beams...of course, in bad lag, the laser could be behind you about two meters and then BOOM, you're laundry.
In summary, the Charger is very powerful in the right hands and very bad in the wrong hands. Just like several top-tier Smash characters I know...