I have to concur with Eagle on the subject of the Mesbah-1's effectiveness. Each piece of equipment is only as useful as the sum of it's parts.
It's actually somewhat unique in terms of modern VSHORAD because it's static; the emphasis in most modern systems is on mobility since this translates into survivability against weapons like the HARM. Iran however has based it's AD-network around "islands" of relatively short-ranged systems like the HAWK and HQ-2 entrenched in semi-hardened facilities supported by handfuls of 23 and 35 mm guns on concrete pads. For better or for worse, the Mesbah-1 fits in pretty well with this strategy.
There's no point in making the Mesbah-1 comparable to the SA-15 or SA-22 in terms of mobility because anything they'd be tasked with protecting wouldn't be moving that fast anyway. The role of the Mesbah-1 within Iran's IADS network is to protect air-defence bases from the inevitable SEAD/DEAD which would be directed their way, which, as Eagle pointed out, just happened in Libya. Thusly because mobility can't be utilized, everything has to be invested in making sure cruise missiles and PGMs can't get through. We've already seen this strategy to some extent utilized in wargames surrounding strategic sites which utilize waves of radar-guided AAA. It's actually antithetical to much of the grand strategy utilized in Iran's naval and ground warfare doctrine which emphasizes mobility and passive evasion (for instance, look at AShMs) which I think is extremely odd. Then again, it does fit in well with the idea of localized defence nodes that are independent of larger networks for protection.
This explanation puts a couple of things I've been thinking about in regard to the Mesbah-1 in a different light:
I was rather surprised that the radar and EO system were mounted in separate vehicles since in most modern systems they're mounted coaxially. Putting it on a separate trailer means another truck to tow it, another generator, more time spent setting it up/taking it down, and so on. Even the Skyguard has an integrated EO/radar trailer. Likewise, I've been wondering where the engagement radar is. Most of the radar-guided AAA systems I can think of off the top of my head use both an engagement and acquisition radar but we have only seen one here and I'd wager it's a general search radar because of the way it's mounted and traverses. Interestingly the same is true for the Samavat (though since we only ever saw one picture of it's radar it can hardly be called conclusive). Maybe the optical system is the primary engagement device rather then simply a backup in case of jamming as is the case for many VSHORAD devices today. In this light, putting them in separate trailers makes perfect sense because mobility isn't expected anyway, and separating the components adds in redundancy to SEAD/DEAD that would be absent if they were both co-located. Permanent passive engagement means that even in event of a successful HARM strike the Mesbah can remain in the battle with just the EO device.
With regard to the identity of the radar, I've been doing some more fishing around and a number of radars that have the same basic configuration of antenna with long horizontal plates arrayed in a column, are given this characteristic shape by using planar array waveguides. (I'm thinking particularly of the 9S18M1, pictured here
). It might be what we're looking at here in the case of Mesbah. I just wish I could dig up information on how the FB-6 actually functions.