I think it's just a case of gearing up Rey with the latest gears provides a huge edge out of the gate. She gets over 16k health and protection and is hard to take down before all hell breaks loose. And now her increased damage is just enough to kill lower geared toons while RG snoozes. Especially paired with Phasma who is guaranteed buff, because phasma is a TANK! But once most of your own toons reach higher gear, she will be normal Rey, again. Presumably. Same for 555's.
In the end, balance will return. EA pays people to test this stuff. So don't freak out, just yet.
Due to how Rey works, for her to remain relevant at higher level, higer gear Rey necessarily wrecks the snot out of lower gear teams.
Besides. Without high gear Rey, RG and 555's around to get the rest of us all twisted up, we would have no reason to jones for the latest purple jewelry. These toons make the gears go round. And they're just the beginning.