You might want to add some active sensors so that it can actually shoot at things. The surprise of having it pop out of nowhere might become more of a mild amusement when its only usable weapon is a staring contest. Otherwise, though, it looks quite cool, if expensive (as cool things often are).
it has thermal sensors, and although they are not the best, I think they are good enough, also, its meant for defense of populated sistems, which in turn means I will have several deep space tracking stations and a couple of missile PDC's that come with powerfull sensors of their own, so I think this pretty much ofsets the disadvantage of not having active sensors. Also you cant be stealthy waving a huge flashlight around. when you are going stealth and are using active sensors, you need not to put the ative sensor on your fighting ship, but rather on small (or tanky) scouts, away from the stealth ships or else you might just be caught on missile sensors and lose the element of surprise.
your criticism is very valid, and if it were to operate solo I would agree with you, but considering the role this ship fills...
I might make a non-stealth version too... with long range and huge sensors, and lasers instead of railguns! swipe all missiles away savagely charging head on... sounds just as fun as stealth.