One question about this:
I killed the boss of the starter quest for my temporal warden character, but could not find a temporal rift on that level. So I used the Timeport: Point Zero skill to return to Point Zero. Did I miss out on completing the quest successfully?
I'm pretty sure you're boned and need to restart the character, unless someone else knows something. As with all starting characters, part of the reward for completing the quest and defeating the initial zone is the Rod of Recall. If you recall to Point Zero before killing the boss of the starter area, you won't get a shot at the boss that drops the Rod. Theoretically, you could beat the game without it, and it might even be a fun challenge for an advanced player, but otherwise, you need to complete the quest without returning to Point Zero via spell.
If you really couldn't find the rift (did you use autosearch? that'll always take you to the rift in the end, once the level is cleared out), you should probably report that as a bug. Keep in mind that the final one only appears when you defeat the Queen.