Yeah Cyborg's ranking has a ton of qualifiers but you can't ignore that she spent 10 years on top and undefeated, even if that was almost all vs. blown up cans and pissing hot during that time. Testing positive pre-USADA in Strikeforce is pretty damning - that means she pissed hot on fight night and didn't even try to cycle off or keep up appearances. Then there's the whole issue of the 6 lbs bikini when she missed weight. Cyborg has had a great run but she's really tough to root for as a fighter.
What Kayla is doing in Strikeforce is basically what Cyborg did her whole career and if she keeps doing it for another 7 or 8 fights with maybe 1 or 2 former UFC contenders thrown in the mix (without testing positive or missing weight), IMO she'd have a case to take Cyborg's place in your ranking.