MoP and WoD both had legendary catch up mechanics; however, if you started late in the expansion a new player would never fully able to catch up to someone who has played consistently all expansion. That's the reward for playing consistently.
With that said, I do think alts need some sort of accelerated progression with Malefic Cores. Like, once you have a fully resistance capped cloak on one toon, you can purchase them for echoes on alts, or something.