That was I believe my 200th magic jewel draw in a row without an SSR, and I'm up to 30 premium draws on the same losing streak.
Last SSR I got was last year. I think the game decided I have played too much and should be encouraged to stop. ;-(
I just spent about 2 and half hours watching scenes and doing battles to build back up to 3k jewels, and all I got was a single SR eidolon and 9 Rs. I was so excited, what a waste of time...
So now that's 15k jewels I spent trying for Diabolos and Amon, and not a single one of either. Only SSR I got was an Osiris dupe. My notorious bad luck continues... I did get an extra Fleurety copy, but that doesn't make this worth it.
Finding a single SSR in 15k Jewels isn't bad, it's about average. Your expectations are completely off.
Also, reminder that Diabolos is (the weakest) P2W Eidolon, so it comes at the average of 420k Jewels or something if I remember right. That's 1/8 chance, so ~3360k Jewels for Diabolos. With the rate up, it's maybe about ~2240k. Reaaally rough numbers here, but come on, finding her with 15k is just... a liiiiiiiiiiiiiiiiiiiiiiittle bit too optimistic.