I disagree with spending points in CON because you can compensate with HP bonuses by gearing toward those bonuses.
For example, let’s take your calculation and add a few things to point out my case.
7700 base HP + 1805 from Mastery = 9505
Now let’s take the Grynas Set as an example. The set give you 1020 HP + 430x 2 from boots and gauntlets. That’s a total of 11385 total hp. Take in consideration this set is not end game and we are not considering gems to boost HP further.
In regards to blessing, I mentioned this guide is not meant for optimal leveling. Those three points you spend in Blessing are better spend somewhere else. Regardless, thanks for your opinion!