I never actually read all of Diurnal and Nocturnal Sect's text. I just saw, "Blahty blahty blah Regen" or "Blahty Blahty Blah Shield." And my first couple of runs after getting Nocturnal Stance left me unimpressed so I just stuck with Diurnal. It wasn't until leveling in the Library someone said something. It was a tank and he said something along the lines of, "Stop using your DPS stance." I thought he meant Cleric, so was Ok. Then near the end he said something like, "If you're going to stay in your DPS stance at least DPS." I thought he was crazy so I just went with it. Then a couple of days later someone else said something along the same lines, but actually mentioned Diurnal and Nocturnal. So I actually took a closer look and noticed Diurnal had a 5% Attack Speed increase and Nocturnal had a 5% Healing Potancy Increase. Whoops.

Thinking back, people have probably said something about it before, but I just assumed they meant Cleric Stance.