"If will-o-wisp missing" is your argument that you can't beat e-killer, than you might as well say it has no real counter. Giratina still gets 2hkoed by a +2 shadow claw and if it misses will-o-wisp then rest-talk isn't going to save you. Terrakion can't safely switch in due to the threat of EQ or brick break.
In such a fast-paced and dangerous enviroment that ubers is, missing a crucial hit will lose you a pokemon anyway and that's one of the reasons why lum berry e-killer is good.
A man can no more diminish God's glory by refusing to worship Him than a lunatic can put out the sun by scribbling the word 'darkness' on the walls of his cell. ~C.S. Lewis