sser
First off, we should establish that Hearthpwn's data is just how many are used in the decks on their site. They don't have a direct connection to Blizz's data or anything like that. As a result, while that is a mighty high number, it's not explicit proof of that much. I would also point out that 32% on Loatheb is also quite high, and Loatheb is by no means overpowered really. Piloted Shredder is also sitting at 36.6% on hearthpwn's stats.
Sub 7 has always been a thing. People ran BGH in their midrange decks to handle Handlock. A lot of very successful druid lists ran 2 BGH before the days of GVG. It's worth noting that BGH doesn't actually explicitly counter Dr. Boom. Yes, you essentially gain 4 mana on your opponent from the exchange (or less, depends on boom-bot rng) but it's not as much of a hard counter as, say, BGHing a Rag.
I also want to point out that you've opened up a very interesting dialogue here. Going off of Hearthpwn statistics, we can see interesting things like
Within Druid Decks:
Keeper of the Grove: 82%
Ancient of Lore: 66.9%
Druid of the Claw 65%
Within Paladin Decks:
Consecration: 87% of Paladin decks
Truesilver Champion: 85% of Paladin decks
Tirion: 54.5% of Paladin decks
so on and so forth. obviously, boom's usage on hearthpwn IS very impressive, but it should be noted that there are many cards that are clearly more "auto-include" than Boom.
tl;dr - Hearthpwn statistics don't really mean that much, and yeah, Boom is certainly a very strong card, but I still don't think that he's warping the metagame in a negative fashion, and it seems clear that Blizzard's data agrees with that.
Addendum - BGH is also sitting at 26% on Hearthpwn. That shows, at least by that metric, that while BGH is very popular, there isn't 1 to 1 correlation of BGHs and Booms or anything like that.
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