First let me say that this is a really well written article, it's easy to read and concise to it's points.
There's just a few small bit's it's like to criticize if I may:
The consistency section while explaining well that consistency is the likeliness of your deck pulling off it's core strategy each game to support this the only information given is that of specific consistency cards, while obviously important as the backbone of the deck there's 2 other points to keep in mind when thinking of consistency:
1. The count of each specific card - This is touched upon in the Balancing section but it should be noted that balancing the amount of each card is a process to aid overall deck consistency as you need to be able to access key cards when you need them in the game.
For this point it would be highly advisable to run a 3/3 line of HeracrossEX rather than 3/2 as you don't want to be missing the mega drop and you can't rely on always having Ultra Ball to search it out so having more chance to draw one even if you won't end up using 3 adds to deck consistency.
2. Reducing clunk - I always like to use the saying 'you can make good use of any card that's put into a deck, but it doesn't mean it needs to be there' - Ultimately this means that you could throw any card into a deck that has a good effect and make use of it when you have it but if it doesn't specifically support the deck or fit with the specific core plan of the deck (barring if it's a tech for a specific threat) then all it will do is reduce consistency as you will draw it when a core deck card would have been preferable.
From this point I wouldn't suggest 3 of the cards in this deck:
Professor's Letter
Sacred Ash
Startling Megaphone
You're attaching 1 energy from hand per turn with this deck, although making sure you have energy in hand to attach would be nice, there's plenty of hand refresh in this deck that you should be drawing into 1 each turn.
As you say you won't need to use more than 2 M HeracrossEX in the game and 3 Dusknoir is definitely enough to be able to get out 1-2 each game, yes you could put some back in that you discard with Professor Juniper/Sycamore but to me it just aids sloppy discards, yes there are some games where you're forced to discard pokemon that you don't want to but it's better to just adjust for the situation rather than rely on a card that equally could get discarded earlier or be prized and that is going to be drawn over something more useful in the majority of games.
Getting rid of the opponent's Tools is nice but there's nothing specifically hurting the strategy of this deck that you need to run it for, it just adds to the clunk, it is going to be drawn over a more useful card and isn't needed to make the deck function or counter a specific threat.
I'd also like to make a note about VirizionEX, on first glance it's easy to think that as it accelerates Grass Energy and HeracrossEX needs Grass Energy to attack that it just fits but if you break down how you'd like a general consistent game to play out then VirizionEX doesn't perform much of a function.
Let's say we open with VirizionEX, we use our turn 1 to get a HeracrossEX onto the bench and attach an energy to VirizionEX, next turn we want to be mega evolving the HeracrossEX, this will end the turn so we won't get to attack with VirizionEX and thus attaching here would be meaningless, but if we start attaching to HeracrossEX then we're essentially a turn behind on it's attachments.
As stated HeracrossEX is bulky and won't be KO'd easily, adding to the fact that this deck is designed for healing the HeracrossEX, it's much more viable to see the turns play out like this:
Turn 1 Attach to HeracrossEX and pass
Turn 2 Attach again to HeracrossEX, mega evolve and pass
Turn 3 Attach a 3rd time and start attacking.
At this point the game plan will be to prioritize Dusknoir while also starting to build another HeracrossEX, both the 3rd attachment of the first one and the new one are aided by Mega Turbo, not for speed in this case but for consistency.
In light of this removing some cards and adding in a M HeracrossEX, 1-2 Rare Candy and a Duskull to me would greatly aid consistency and still have around 6 spaces left to play around with.
Apologies for this turning into such a long reply, I don't mean it to be a rant against your article, it is very well written and informative, I just felt the need to add my own thoughts so that hopefully it will be of use to new players.
