You got the "primary stat" right. However, endurance is the number 1 stat for any and all classes really (not just for tanks, as you say).
I play IA Operative. Cunning will make me do more damage, and it will make me heal more. But I can't do any damage if I'm dead, and I can't heal anything if I'm dead. So since endurance makes me not die, Endurance is the number 1 stat. Cunning is 2nd only.
For most people, the primary stat should be fairly obvious, since most of your quest gear is aimed towards this stat and also the PvP armor that is class specific etc. But nice of you to write a guide for those that didn't notice the hint.
The OP was correct when he said that endurance is up to the player. Some folks like playing high DPS 'glass' cannons. Other folks stress 'survivability' over everything else. I personally take the middle road. The quicker I kill the mob, the less damage it will do to me, but bad pulls happen. I'm also a healer and threat mechanics aren't completely understood yet, so better safe than sorry.