I followed the link past the Mecklin article - which is short on detail - to the Theodore Postel interview and was surprised to find that his "expert" opinion consisted of the claim that "the Iron Dome system is not working very well at all" followed by the "guess" (his word) that "maybe" (his word) it was "working 5 percent of the time." This rigorous and scholarly analysis was in turn followed by the very scientific words "could be" prefixing the statistically precise "even less."
He then went on to claim - in response to a leading question - that in order to work, the intercepting missile has to hit the rocket head on. He offered no evidence of this, nor any explanation of why this should be the case, nor any evidence of rockets hitting targets in populated areas. Again, He offered no statistics of his own nor did he state whether "WORKING 5% of the time" means failing to intercept 95% of the time after being launched or being launched only in a small sub-set of cases and thus intercepting only 5% of the rockets with the others being perrmitted through because they are not heading towards populated areas.
Finally neither the Postol interview nor the Mecklin article says anything about the opinons of other academic military experts or whether there is support for Postol's conclusions amongst his peers.