Some analysis of the new Vaoreon (TL;DR: Blastoise is still too inconsistent, but 4x basic EX + Varporeon may have legs)
I created a post yesterday saying I think a lot of the newly-previewed cards are overrated, and the most common disagreement I've seen is for the new Vaporeon, which has a power to freely move energy from benches water types to active water types as often as you like.
The general argument is that Vaporeon will allow you to escape with damaged pokemon and move all their energy to a fresh active pokemon without giving up any prizes or tempo.
However, the cards involved in this are at a minimum: 1) A starmie EX as the initial pokemon, 2) a Vaporeon with its power active and 3) a new fresh pokemon to put the energy on. At a minimum, this is 5 cards, and my intuition is that this is pretty unlikely given the speed of games.
To that end, I have created a simulation asking how often, by the 3rd to the 5th player turn, does a player have all the cards in hand to make this work? I've done it separately if the last card is a basic (Articuno EX), a stage 1 evolution (another Starmie EX), or a Stage 2 (Blastoise EX). The simulation does use pokeball and professor oak and assumes 2 of each in the deck.
The results, the % chance of having all the necessary cards in hand by turn X, are shown below.
In short, by the 3rd turn (the earliest you could have a stage 2 out if you went second), you have a 13% of having all the cards in your hand. So if you go second, and try to retreat starmie after it's eaten hits turn 3 + 5, you only have a 13% chance to send out blastoise and put your energy on it using Vaporeon's power. If your backup is instead Articuno EX, this goes up to 35%, which isn't terrible, but certainly isn't reliable.
If you let starmie take one more hit (or go first and it still only eats two hits), your chances go up to 22% for blastoise and 50% for Articuno, which is at least as good as a coin flip. Finally, if your starmie EX lasts another turn (eating 3 hits if going first, 4 if second), your chances are up to 46% (almost a coin flip) for Blastoise, and 67% for Articuno.
After running these numbers, I'm more convinced the new Vaporeon is at least decent. Blastoise I don't think gets enough of a consistency boost to be useful and takes up too much room in the deck. I think what might have the most legs is only Vaporeon + Basic EXs (Lapras or Articuno). With a deck of 2x Lapras, 2x Articuno, and Vaporeon, you have 50% of having everything on your 3rd turn, a 67% on your 4th, and a 74% on your 5th (data not shown). That's reasonably consistent, and combined with Misty, gives some decent chance of having both a strong opening and a strong grindy finish (especially with Lapras EX). I think I'll at least try that deck at some point, especially if some of the Pikachu EX counters shown in this set reduce its dominance.