You know, the hardest part of clearing something like the Thaumaturge Hunting Log is when you have to face fast-moving melée enemies. The 3rd Cohort Secutors are the Pugilists of the Garlean Empire. You’ll find them in the area of Larkscall that’s just below where it says “Sylphlands” on the map.
You only need two Secutors, which is good, because, I believe, there are only two. Respawn around here is fairly quick in case someone went before you.