It takes like 10minutes to do Rank 1 or Rank 2 hunting log, maybe 15-20min to do a Rank 4 or 5. With teleports and mounts and companion, it's very quick filler, especially between queues. It's also great for when you're within 25-15% of leveling up, completing a rank also gives a large noticeable chunk of EXP. Less noticeable 35+, but not insignificant.