Are rebel fleets still top 10 competitive?

You can still get to the top with a Rebel fleet. How practical It is, how many battles you need, will depend on your shard. I can get through 7 star Negotiators and 6 star Malevolences with:

Home One - AA G12+3
Han's Falcom - r4 pilots
Biggs XWing - G12+0
Bistans UWing - G9 Pilots
--
Phantom - G12 pilots
Ghost - G12 pilots
Cassians UWing - G12 pilots
Houndstooth - Bossk G12

Your mileage may vary...