The reason the old system would be great is that is player proximity based and very responsice to players. Having it stack 1 every minute would cause a problem of punishing low player count instances with longer kill times than a full 72 instance.
I wonder why they didn't just do it again(another good implementation from past exploration content they decided not to use in OC).
There's been some good overall QoL for overworld activities in Exploratory zones that would have been great additions to the general overworld maps like NM's, Duels, CE's and random chest spawns. It always one of the biggest disapointments for me to come out of expansion releases when they dont take what was neat from those zones and use them in the rest of the game.