Well, I suppose one could argue that getting some packs or even cards, as Stonekeep has noted, might aid you in subsequent runs:
The Common card might seem like a silly reward, but if you haven’t pre-ordered and you rely on free packs to play this Brawl, you will certainly miss some Commons, so that reward MIGHT give you a useful card you can play in another run.
There is also another passage from him I’d quote:
All of that said, would I recommend playing it? Well, yes, and no. I think the biggest elephant in the room is the Brawl being “P2W” and kind of luck-based, depending on the cards you open. Players who don’t pre-purchase will be put at a heavy disadvantage compared to players who do. Even among those who pre-purchased there will be a big disparity. Yes, pre-purchase will give you all of the Commons and Rares, but not Epics and Legendaries. One player might open the strongest ones while another might get something completely useless. Of course, we still don’t know how the Brawl meta will look. Maybe some of the strongest decks will only run a few GDB Commons. Heck, maybe there will be viable decks that don’t even require any GDB cards at all (we’ll definitely try to look for some).
On the other hand, all players will get an entry for free, so there’s no harm in trying it out, especially if you pre-ordered. If you enjoy the Brawl meta or simply want to try to gamble some Gold for extra packs, then by all means, go ahead. I can recommend it much more easily than the Heroic Tavern Brawl.
However, this also reminds me of their signature way of ‘trolling’ F2P players. For example, I was thinking of Mercenaries in particular (sorry if that’s not your cup of tea, but that’d be my specialty and what I probably know best): some bosses drop ‘coins’ for mercs (primarily expensive ones) that they are supposed to be weak against (e.g. Avalanchan/Ragnaros, Ursula/Thrall, Icehowl/Alexstrasza, Garr/Jaina respectively)… So if you’re a P2W ‘whale’ and already got that merc from the packs you bought, that’s supposedly good for you, but if you’re farming the boss to actually craft that legendary merc — well… Of course, you don’t really need those mercs in order to farm those bosses quite effectively, but the perceived design logic there is… peculiar.
I’ve just been doing some research of sorts, related to this question, by reading this article:
https://www.hearthstonetopdecks.com/what-decks-will-be-playable-in-the-great-dark-beyond-pre-release-brawl/
Of course, it’s pure ‘theorycrafting’ at this point, but if those packs turn out not so impactful in terms of performance in this brawl, then the joke will be on those ‘whales’ indeed.
I understand not buying packs, but not even opening some occasional free ones from reward tracks, tavern brawls and such?
(Updated, expanded a bit)