For now I'd say give it a little time for the community/playerbase to catch up - many players who are now playing the game on BGA, myself included, have not played much or at all in person or anywhere else. And trying to remember or absorb the rules while reading all the cards + effects, and then implementing that info into a strategy, is not fast.
Another thing you can control for besides the timer speed, is opponent rating. By setting a rating minimum of 100 Elo you can guarantee that the players have played at least a few games on BGA already, and by setting a rating minimum of 200 you can guarantee that even more experienced players are at your table. You can also put a custom message on the table such as "please play fast" though many people who join probably won't read it.
