Maintenance for the week of January 6:
• PC/Mac: No maintenance – January 6
• NA megaservers for maintenance – January 8, 4:00AM EST (9:00 UTC) - 8:00AM EST (13:00 UTC)
• EU megaservers for maintenance – January 8, 9:00 UTC (4:00AM EST) - 13:00 UTC (8:00AM EST)
I waited 20 minutes for boss to spawn, and the screen says that I'm in combat--borders are flashing red--but no boss is present. This was supposed to be fixed with the last maintenance patch, so just wanted to alert the devs.
It appears that the delve boss is not *respawning* correctly, but it does spawn in the first time in an instance. So for a workaround until the incremental on the 14th, you can try what I did, which was to periodically go into the delve, go straight to the delve boss, and if the boss isn't spawned, go do something else for a while and try again. Don't bother waiting around if it's already been killed in that instance, it won't respawn. You need to get into an instance of the delve where the boss hasn't been killed yet, and since the delve population max is pretty small (I think 6?) it's easier to get lucky and be the first one into a new instance.