It wasn't nerfed /because/ of the shield attack. DS needed a nerf because you cannot chase her by any means, you cannot hit her while moving, and it's rare you'll even get a hit in if she's recharging. It does allow players to flank the boss, possible to take her by surprise and get some decent damage in. Of course, the mindset of almost every firebug is jump-jet and simply charge head on, so it won't be seen that often I'd wager. A slight increase in speed would mean nothing other than avoiding other bosses. DS moves at five times the speed of the infiltrator, or just about I believe. Could be wrong.