We're roughly the same age, the same gender, and have very nearly the same resting heart rate ... and your HR profile looks very similar to many of my rides. So I don't think it looks extreme at all.

Here's the link to my motionbased HR data for a 7 1/2 hour, 50 mile MTB race. Mind you, I was PACING myself for an all day ride, and I still averaged 166, with a max HR of 187.

MHR varies significantly by individual, so don't get concerned because you don't think you represent the norm.