If I'm remembering this deck correctly, the idea is to use Mew Prime's See Off attack to put a Gyrados SF into the Lost Zone. From then on, every one of your Mew Primes are able to use Tail Revenge due to their Lost Link Poké-BODY. You get Magikarp into the discard pretty much the same way regular Gyrados decks manage it - Junk Arm, Regice, Volkner's Philosophy, and the like.
The advantages are that you only need to recycle a single basic, your damage cap is 120 instead of 90 since you don't need a Karp under your Gyrados, you don't need Broken Time-Space at all, and you can still function as a regular Gyrados deck in a pinch.
Your disadvantages are that Mew Prime only has 60 HP, so it needs both Snowpoint Temple and Expert Belt to have even a semblance of durability, Dialga G LV.X laughs at you, and you actually need a Psychic Energy to set up.
Post-Ruling change, MewDos is probably too slow because it needs to take at least two turns to set up, while its competitors are working on either instant setup or disruption. Especially post Black and White, where while you still need two turns of setup even in an ideal world, Zekrom can go off T1.
