You're entitled to your opinion, but I'm not sure how you've never had that one party member that just drags the team down because of RNG not triggering and slowing everyone else down in the process. With Saras in first position, she's guaranteed to hit 90 burst in time, and the ability to pull that slowest member up to the rest of the team can be a huge difference (due to the way full burst triggers, this is often the 2nd to last hime to 70+, while the last is fine at 60). I've used Saras for a long time before I pulled Osiris and she's way more useful to speed the team up than your theory crafting may suggest.

Also, while she certainly can't help fully tanking AOEs like true defense himes, she herself can be extremely tough, and can help guard and heal a valuable 2nd target. This is actually quite useful when enemies suddenly decides to focus down one particular hime.