The problem was wotlk/cata, everything should be linear.
92(vanilla), 92*2 (tbc), 92*3 (wotlk), 92*3.5 (cata,only 5 levels), 92*4 (mop,only 5 levels).
-> 368 should be the maximum highest ilevel of the last raid in mists of pandaria.
As for stat weights goes If we decide that roughly 40-45 is the highest prim stat/ stam on a 92 item then no 368 item should have more than 160-180 prim stat/ stamina.
Legendary or not it should be consistent.
Higher numbers make sense, IMO. It shows just how much stronger you are getting as you play. Do you think 10/25 people with only 15k HP and maybe 2k DPS would have been able to defeat something like Deathwing? Or Ragnaros? No, you need to be this powerful hero to take on the enemies that you do. Otherwise it makes no sense.
Yes, they would have, because the game would have been scaled so that it would be possible. Bosses could have 1000 hp and everyone could hit for 1 damage, or have 100 billion hp and everyone hits for 10 million. They are just arbitrary numbers. Your DPS has nothing to do with how powerful characters are in WoW lore.