The only time a non tanking cloak was considered "better" was when there wasn't a comparable one. For example the Heroic Rhyolith cloak was better than the Quest or Fireland rep cloaks. Same went for Sinestra.
The argument for the sinestra quote was: "you will probably also note that the Sinestra caster cloak is listed on the chardev profile. That isn't a mistake. It has more mastery, a gem socket, more stm, more armor, and only comes at the loss of about .5% avoidance once you reforge the haste into dodge. This is mainly due to them not even adding a 372 tanking cloak and the BiS is supposed to be the Hyjal rep one. Who knows if this will stick or not, but I personally would take the mastery/stm gain over .5% avoidance. "
Bottom line is, when there is a huge difference in I level say 359 compared to 379, then you can start looking at cloaks with int or agility if it gives a lot more mastery. Cuz then your not only gaining mastery but also a lot more stam and armor, and even more of a secondary stat that can be reforged.
It sounds like your "friend" was around for the beginning of cata, and remembers the Sinestra argument boiling down to, the cloak has more mastery then it must be better, and ignored the big picture.