The challenges are pretty fun & challenging. If you want to participate in the hunt for Mindflayer Invaders, they can still be found in any level range of quests. Or just wait until they're all found and help with the exhausting part of it.
The next round could be in a higher lvl range, which could allow you to play with fresh iconic or veteran characters to participate. This round may well take longer if the progression in kills to exhaust a quests continues. i.e. 10 to 30 kills/quest, so maybe even more for phase 3.
Either way, at least it's not a huge lag-fest!