im not even sure if the rares in normal seal are fixed if they are it takes 60 scrolls for a rare ... rare means chio , itachi , konan, daidara, sanins, sasori etc.
and wich one you get ... thats random so if you for example got a sasri ... its another 60 for the next rare.

But like i said im not sure with Seal tresure ... cause nobody actuly draws from seal anymore.

and a little bit to Chio herself. yes taht are a loot of chases she has ... but they do like no dmg at all.
so even if you get her, you need enjas taht do a loot of dmg ...otherwhise you gonna fall asleep while you combo ... and then get destroyed

But there are better ninjas to help you with chakra ... the sages ... 5 kage tenami and Ao for example oreven any orochimaru
thing is chio has to combo before you get the chakra ...means if you are up vs a teamwith paralyse ... youa re done for. if you are up vs anything that cant be comboed ..you are done .

Chio sure is nice in someteam... but there are better ninjas out taht can replace her already