You guys should actually test my list against Metagross before arguing the playability of Policy....
Let me just reason to you a few things and you're welcome to ignore me if you don't care. I probably should've just said this in my first reply to this thread.
1. Have you considered what ratio of the
meta will be playing Metagross GX at a
regional event? I don't mean online, and I don't mean at locals either. I mean the large scale, large sample size events. Even if you take 1 loss to a Metagross GX player, you can still take top ranks at an event by winning most of your other match ups. What you should be more concerned about is how you're going to win your mirror match up, because an estimated at least 1/4th of all players will be running Gardevoir GX and at least another 1/4th of them will be running a Garbodor variant. It's probably more like 1/3rd of players will be running a Garbodor variant, really. Unless you can say for absolute certainty that you're going to run into Metagross GX more often than another Gardevoir GX or Garbodor variant, then I see little reason when you can take an auto loss and still take top at an event.
2. Are you 4-1 in
Swiss rounds against Metagross GX, or are you 4-1 against 5 different players with 5 different deck lists who did not expect you were running Weakness Policy? Do you even in know if the players you're playing against online are playing Metagross GX competitively? For fun? For the first time? Online is not the most competitive environment available. In a best of 3 scenario, if your opponent is smart, he/she will change his/her strategy in order to make sure you don't get to keep them in play, or simply work around you by using Necrozma GX's GX attack, and Weakness Policy won't mean anything anymore.
3. If you want to talk about match ups, Metagross GX may be the one counter to Gardevoir GX, but Garbotoxin Garbodor, Greninja's Shadow Stitching, and anything fire are all direct counters to Metagross GX as well,
except they don't have to change their deck lists at all in order to beat Metagross. Metagross GX is completely banking on the probability of there being an astronomical amount of Gardevoir GX players, but against any other match up except maybe for Tapu Bulu GX/Vikavolt, it's got nowhere close to an autowin. The lack of other very favorable match ups is the main reason why Metagross GX will not see extensive play.
The issue with Weakness Policy is that it
does not guarantee that you will win anyway, and it only gives you relief for one match up in the ENTIRE meta. You have to think about a strategy for winning the entire event, not for beating one match up, and if a majority of players in the meta are playing Metagross GX at regionals, I don't know why you would take Gardevoir to begin with.