Many of the Greyhound buses from NY to Foxwoods are 'local' meaning there are lots of stops and it can take 4 or 5 hours to get there when it really should take 2.5 hours max. They have pretty nice buses (WiFi, electrical outlets, comfortable seats) - but there is a major drawback.

The main company that goes there is Greyhound from Port Authority. Too late for the OP, but perhaps my answer will help someone else who - like me - travels to Foxwoods by bus from NYC.