It seems like these abilities suppress each other, which is extremely frustrating. I was toying around with a ranger-group party (3 rangers, cipher, druid, chanter) and tried using Marked Prey from all of them at the same time. They all cast, but only 1 works (and only for the ranger who cast it; the other 2 get no effect).
Pretty lame, and it seems like Sworn Enemy also interacts with Marked Prey in terms of suppression-
https://forums.obsidian.net/topic/90384-sworn-enemy-supresses-marked-prey/?hl=%2Bmarked+%2Bprey
I just tested it with my normal party, and in this case Sworn Enemy was Suppressed by Marked Prey