@BobaBing Don't need to be incredibly fast. 480-520 range is fine. You ideally want to be around 120k health and 11-13k damage depending on what triangle you're running (CD/Offense primary). You can also run an offense primary arrow with decent secondary speed.
Against GL Rey you want to run SLKR with ST, KRU, Hux, and either FOO for the full first order bonus, or Thrawn for crowd control.
Depending on the team:
Stasis Strike (aka "Poke") someone who can be stunned. Usually it's GAS or Handbag Finn.
Use Hux to pass back to SLKR.
Poke someone else who can be stunned.
Use FOO to pass back to SLKR. If you have Thrawn, fracture Rey instead. It'll help boost you towards your Ultimate (if you have it unlocked) because it does damage 4x with each one potentially Crit hitting.
Furious Onslaught (aka "Swipe/Swish") with someone who's stunned as the primary target. He drains double the mastery from stunned targets. It's excellent against GAS or JKL because after 1-2 AoEs their accuracy is in the toilet and they can't hit the broadside of a barn.
Against Rey the goal is to have your ultimate fully charged to 100% around the time she enters her crossed stance. If you have at least 3 members standing SLKR will survive. Then you do your ultimate. In your Aggressive stance you'll want to swipe twice, and then for the third move decide based on what the enemy team looks like.
If Rey is the only one left standing and she isn't in damage immunity, or its worn off, then poke. Should end the fight.
If she's still damage immune, I usually swipe one more time to boost my mastery more and take care of any surviving enemies.
Once her immunity wears off, and your ultimate is done, use Stasis/poke to finish the fight.