Red Focus Options For Poison?

How useful is RF for poison considering her EX fireball is pretty crucial? Just picked her up and I had a go in the lab coming up with some RF combos for her with varying levels of success what with the damage scaling.

https://www.youtube.com/watch?v=tVJPw2s1oq4

cr.mk xx rekka RFC is not bad since there isn’t much scaling, but you have to confirm off 1 rekka. Doing 2 rekkas into RFC allows you to confirm the red focus but also the follow up damage is going to be reduced quite a bit. Poison has great EX moves, gets good options with FADC, has an amazing super, there isn’t much reason to spend 3 bars on red focus a lot of times when you can get better mileage off using the bars individually, using an fadc or saving up for super. Atleast thats from my experience.