My biggest question is: how do you make this consistent? The dedenne take up useful space, and you would be better of running purely mewtwo tag.
This deck IS consistent.
Yes, it bricks sometimes, but so does pikarom, blace, and green's.
Dede is important for the deck to run.
In a regular mally, you don't play cherish balls because you don't run many gxs.
Because of this, you just don't run that many dedes, instead you run jirachi.
But jirachi is not as good to get set up as dede is.
In a malamar deck, the main goal is to get set up.
If you get set up, you win. If you don't, you lose.
Jirachi only gets you 1 trainer at a time, but multiple over the course of the game.
With dede, you get way more cards, just only for 1 turn.
Because of this, dede is better if you want to set up FAST.
But to make good use of it, you have to play cherish ball.
Something that most mally builds don't do, which is understandable.
They can't play the dede engine, even though it's better.
This makes them set up less consistently, which makes them lose more often.
This is why I play dede over jirachi.
Jirachi is good and all, but in THIS specific deck, where you need 3 inkay turn 1 and 2 mally turn 2, dede is better.
Dede also discards cards which helps get energy in the discard. Another important thing you need turn 1-2.