I have done this fight three times after 7.0 dropped and the first two times she gave me no issues. On the third character, I finally ran into this issue everyone has been talking about. The first two attempts where with melee characters with gap closers. The third was with a ranged smuggler. It seems when she splits into multiple versions of herself is when her overtuned damage comes into play and I started having issues. It helped to quickly try to close the gap an attack her to stop her having duplicate versions of herself as quickly as possible. The smuggler was able to attack quickly but still took lots of damage. However I still died eventually, It seems the only reason I beat her at all with the melee characters was that she had glitched in place and never did the duplicate thing. It took a few tries with the smuggler but she eventually did the same getting stuck in place attacking my companion glitch and I beat her that way.
Maybe now with the fixed companions it might be better. Hopefully they do fix it like the purifier droids the just fixed instead of having to wait for a glitch to trigger to get past their own bug. It seems they also tuned the Spirit of Vengance flashpoint by reducing enemy health. I remember also dying a bit there recently when too many mobs surrounded me sometimes and I had to resort to kiting them at points.
If they did not fix this Gemini fight, this makes me think the also did not fix the issue on the Imp side during Onslaught with Malgus in the Ossus library that also caused me problems a month ago. This is a similarly overtuned encounter. That at least if you die the mobs you kill stay dead and you can progress by just dying and slowly advancing through the quest and once you get the bosses you have to kill by themselves they are no problems. Also in that issue stealthing past the mobs you don't need to kill helps, but you still have to kill a few boss characters that are in groups that will melt you and your companion.