I will say even though the Shiva B is counterable(is that a word?) it should have its price raised to SKN. It is too much of a "Iwin" button to be at GC level
I don't think a price increase is enough, it needs to be changed.
It's only counterable if the pilot screws up. As taemien pointed out, there's not a lot of reason for it to drop below 1200 metres most of the time. Narcing is probably the only exception to that and does leave it open to AA fire, but with passive radar it isn't too hard to get within 1000 metres of a target without them noticing you, and then it only takes a few seconds to fire the narc and break off. It offers an observant huit pilot a small window of opportunity, but probably not enough to kill it if the pilot is good.
Not to mention, if getting within 1000 metres is likely to result in death, then the pilot can just choose not to narc and fire the erlrms from 1200+ metres. Sure it's a bit more difficult, but if it keeps you out of harm's way it's probably worth it.
If the pilot gets within 500 metres of anything with an LBX20, he really has screwed up. There is no reason why he should have to be that close to anything on the ground ever.
Using aerospace against it is only partially effective. If the shiva breaks off and runs back to base on full afterburner, it'll likely make it to the cover of the turrets before the enemy aerospace can kill it. Which means it can't kill anything of course, but if the AA aerospace doesn't hang around to keep a constant eye on it, it can just sneak out again with passive radar and get another run off before it gets noticed. Playing AA aerospace against a shiva isn't about killing it, just chasing it around constantly so that it can't kill anything else. I guess that's a counter of sorts, but only as long as the shiva pilot gets bored and takes something else before the AA aerospace pilot does.
Personally, I think the narc launcher and the BHP should be removed from that shiva. It's already got as much firepower as the best ground based LRM boat in the game, with the added bonus of an extra 500 metres range. Without all that stuff it'd still be able to swoop out of nowhere and deliver a devastating barrage from 1000 metres away, it'd just mean that it'd need a ground based narcer to make full use of the range of its erlrms, which is only fair I think.