The guy who played Nick was incredible, I remember thinking he was the biggest prick in history which is testament to his acting skill But then he's the head of a fire station, an extremely responsible job in which every mistake lands on his shoulders whether he caused it or not, maybe he should have indeed been harsh
Thus why even if Nick and John are not having a ruck at each other, Nick always had done what’s best for him as he takes the majority of the responsibility of the watch and their responsibility to follow directions from anyone higher than them including their Station Officer and Sub Officer.
Geoff always followed orders, although he mellowed out over time. Colin was a bit of a hothead when he started but also started to settle into the job at hand, whilst Billy was a good firefighter, he was often a bit too cocky, like he is being here.