I am running Android 6.0 Marshmallow on a non-rooted Asus Zenfone 2 ZE551ML with stock ROM.
It is not possible
Quoting MacroDroid developer, in future request (dated 21 Feb this year- you can access that from within the app in forum )
WhatsApp has no SDK/API by design, they don't want third party apps interacting with their service.
When the automation app can't interact with WhatsApp, it obviously cannot set up automation tasks
I am not conversant with Tasker, but the limitation should be equally valid for any automation app