Advanced cloaking device is over costed.
It never ever gets any use, every time my sigma squadron pilots are destroyed by hlc fire before they can shoot and cloak.
You're right in that it serves no purpose on a Sigma. It really doesn't have a place on either of the generic Phantoms. It belongs on Whisper or Echo along with Veteran Instincts. Which, I agree, makes it prohibitively expensive. The balancing factor for Phantoms is that they perform best with a number of pricey upgrades.
It's certainly ideal on Whisper or Echo with VI, but it absolutely has a place on generics. A free action that gives you two extra evade dice and super mobility (as Wonder Waagh hinted at) is well worth it and useful on any of the phantom pilots.