One of two things, or both possibly:
-
Time of play
If you play at odd hours as compared to the bulk of the community, wait times will be longer, for pretty much anything in the game. -
PvE gets lame quick
Probably a personal thing, but I know I get burned out of pve events within the first week. Playing vs bots just isn’t fun… and I’m guessing other people feel the same way as queue times have always gradually gotten longer over the course of the event.