Personally, I really like the surge stealth drive after impact. It gives surge time to actually kill, the target he emped. Just remember, surge did not have a stealth drive when he was first released and he sucked really bad, so they buffed him. He is one of the most powerful mechs and they should not nerf him. If they nerf him them some other mech would just become op. And for tengu, his stealth drive is to also let him finish his kill, and for dodging. Surge and tengu instantly become prime targets after activating their abilities because they are scary, but without the stealth drive they would just instantly get killed.(because who doesn't like the feeling of thwarting a surge or tengu's ability.) The stealth drive does not effect only the target because the target is the only one who cannot kill him. You have to remember that some mechs are meant to be sitting ducks after activating their ability. Ex: zephyr is super weak after his ability usage but he is designed that way because he is not p2w. Do you see a theme here? Surge-p2w, tengu-p2w, guardian-f2p, zephyr-f2p, killshot-basicallyf2p. Surge is designed to overpowered, and tengu is designed to be an ambusher mech that once he makes his move-you're done for.