Stanks are hard to spot, but it is already compensated by their lack of endurance and speed. Conclusion: Not overpowered at all, considering their price. Increase endurance/speed/weapon range proportional to its spotting range.
The SBH is a bit too stealthy for 400 credirts, this is a ''boss-type'' stealth if you ask me. If the price remains fixed, it should get a specific drawback(e.g. no sprint, because of a cloak that limits movement) at this spotting range.