1. Stronger mobs with lower health.
Make the combat actually interesting, not just bashing your face against a health wall repeatedly. Whose idea was that?
Also reduce the "expected" party fighting these to 4. Free up half the party to help in other ways.

2. Change the "tracking" system to actually be tracking.
Give each party one specific "target" mob on the map that will spawn their next NM. When you kill a mob, have it tell you how far away your target is. By killing a couple, you can get your bearings and head of in the right direction to find your mark. It makes the hunt engaging instead of just zerging to quickly rush up a counter. Again, 4-man miniboss mobs for normal mobs, and dungeon boss style fights for the NMs.

3. Replace the chest "pops" with mini dungeons.
Currently the chest "pop" spots are fixed locations that take forever to respawn meaning when you get in, they're likely all already taken by some other party. I would replace that with a system that constantly keeps a number of them up across the map as a whole, respawning a new one somewhere else when one is used.

Now, instead of just giving a chest, popping one of these teleports the user to a solo mini-dungeon. Inside is some sort of challenge. A puzzle, a platforming challenge, an arena of AoEs to dodge for a time, etc. Make something interesting. If the player wins the challenge within the time limit, it spawns a silver or gold chest. If they fail, they get bronze.