An flush draw+ openend straight draw is only statistically ahead of a single pair after the flop. Change the villan's hand to either two pair or a set, and you are behind. I wouldn't recommend always shoving in this situation. In any event, you are still on a draw and need to improve to win the pot. You may be able to bluff a fair share of these, but as you noticed in a lower buyin NLHE, there is very little fold equity against some players.