It depends on which revenant you are killing. Lower level revenants have much worse drop chances than higher level revs. There is a drop chance calculator which you can check from wiki (link: https://runescape.wiki/w/Revenant_Spirit) to get accurate drop rates.
I've heard lots of ppl been struggling to get 5th or 6th pet. I personally went +10k dry from 5th to 6th pet but then got 6th, 7th and 8th pets within ~7k kills. Currently at 22k kc and I have cyclop
19-Oct-2019 10:02:40