So I'm confused. Is your casting issue only with Whatsapp and facebook videos? Or casting in general?
With MIRRORING, I have only been successful in mirroring my phone/tablet screen to an Android TV (Nexus Player) and Chromecast. Could never get it to work right on a Roku, and was unsuccessful with a samsung smart TV.
With Casting, I was always successful as long as the device i was casting to had the same app that I was casting from on my phone, ie Youtube or Netflix content. Casting also works perfectly to a chromecast and Nexus player. I dont think I have ever had it fail regardless of not having a specific app installed on the Chromecast or Nexus player..