Safe keeper honestly I think you've mis interpreted it or it has been written in a way slightly unclear.
But I wouldn't worry mate
The feeling you get in takeing down An AT-St is Amazing, not because i fire 3 blaster bolts and it's dead lol (despite many claims and evidence to the contrary we are'nt THAT stupid hehe). The reason AT-Sts are a joy to take down is because it's a grueling experience, to try and give you an analogy.
an analogy woody will probably hate but its the first one that springs to mind.
ok Remember Starship troopers? Remember where they are on teh desert panet fighting away at the regular bugs (regular bugs = storm troopers) and then after alot of battle that big Black bug comes from out of teh ground and starts wiping out whole squads, and suddenly the entire platoon is firing away at it that black bug is equivelant to an AT-ST, They become mini objectives.
now the way the withering fire system works is that AT-St that's wiping your men out, can be taken down in various ways. 1 rocket man popping in and out of cover takeing pot shots at it. Chances are your going to get killed or more of your men are going to get killed in the time it takes to bring him down.
Now add in 2 rocket men, someone to resupply them with ammo, a couple of Heavy MG's and a couple assorted A280, and Carbine/DH-17 users. If they all fire at the AT-ST they are All doing damage and thus bringing the beast down. As opposed to the none rocket guys having to sit on teh sidelines and hope the Rocketmen take it down, Or respawn a a rocketmen (leaving you with a squad of rocket men afterwards which is no good.
Withering fire simply allows everyone to chip away at, just some classses and some weapons are better at it than others.
from the AT-ST drivers point of view, he can wipe out alot of people but if he walks himslf into a mass crowd of people (without wiping them out first) he is'nt going to last very long, so what do you do? Team up more AT-ST's to counter this.
it's truly excellent as you find yourself Grouping up with everything, from various troops and classes, to vehicles such as the AT-ST. You are basically tipping the balance of the scales in your favour with the more people you stick with.
this is the complete OPPOSITE of being able to destroy vehicles with a few shot from your blaster, it's not like that at all, and im sure every single one of our testers will attest to that.