Which again, applies for any class. A competent team/player isn't going to put their battle highs in such a vulnerable situation that they'd get picked off like that. A squishy kill isn't squishy if they're being babysat by a healer, no matter what class it is.
The damage component isn't the only factor (albeit it still is one), but compared to other classes its relatively safe due to it's range, uptime/effective cooldown and the reliability of it compared to those of a melee (which is essentially sticking a hand into the blender) or the other ranged (which either can't be reliably done on the move, has a ranged penalty, or both).
If you were working as a team, then no, a SMN isn't one shotting you. But neither is any other class. That counter measure is not exclusive to shutting down summoner. And just as you keep saying, any other class (not just summoner) will get blown up by focus fire if they're standing off to the side or do not have a healer babysitting them. Between what I just mentioned above and a couple of other mentions, SMN remains one of the most formidable classes to bring into frontlines as of this time for what they can do.
And lastly, you're factoring in playerskill, which honestly has no place in talking about how strong a class is, or balance in general. Every countermeasure you've brought up is not exclusive to countering summoner and doesn't downplay their relative strong-points.
