You got your 18. 3 actual pieces of exotic armour for each class, and 3 exotic class items you get from the factions. That's 6 per class and means 18 all up. It's a -blam!-ing slimy technicality they can point to whenever someone questions them like this. I think the worst part however is that they actively advertised using items that aren't in the game. The Tarantala hunter chest piece was in the trailers, as was the blink warlock helmet, as well as the warlock boots. They lied, practically to our faces, and for the most part it seems nobody cares.