Specs Accelgor is actually fairly common. Accelgor has impressive coverage, creating a fast and hard-hitting revenge killer. Life Orb is probably still preferred, the two main reasons being that it is forced to switch out a lot and thus losing 25% of its health each time it switches back in on Stealth Rock, and it has Spikes which is much better on the LO set.
Band Ninjask however is completely different. It still doesn't hit hard enough, and it is outclassed by other Choice Band Bug types like Scizor and Escavalier. The Baton Pass set is a much better way to use Ninjask as it turns it into an efficient staller and a good way to support team mates. Ninjask also lacks coverage, making the set less ideal, at it hates to be locked into a move. Stealth Rock halves the already-frail bug's health on every switch, so it's ability to switch in safely is very limited.
Specs Ninjask and Band Accelgor should never be used as they deal extremely low damage even with the boost.
So basically, they can't switch in too often or they'll die. Ninjask is outclassed as a Band user, and is much better off doing what does best - Baton Passing. They are both extremely frail, so they are vulnerable to priority and fast Choice Scarf users as well.