Just because a line is profitable (set mining) does not make it the most profitable line.
The problem with set mining in this spot is that the implied odds
you need becomes really hard to quantify. 12:1 is fine when a guy is raising UTG with QQ+, AK. But when a villain is raising a lot of hands, 66 is exactly the type of hand he wants a call from.
This allows villain to raise and cbet against us super profitably, since we can only continue on ~25% of flops. And on those non-set flops we continue on, we have little hope of improving, and we usually only have a bluff catcher that will be easy to play against. Not to mention that his range is more suited and connected than usual when he's stealing, so his ability to be drawing live against a set is better.
The only thing villain has to avoid is shipping us a stack when we catch a set, and bluffing
too much when we're bluff catching. And since his range includes a bunch of weak hands, it shouldn't be hard for him to get away from us.
Idk, I thought it was common knowledge that we don't set mine against wide ranges. To me, the best way to exploit villain is to bluff. 66 is a great hand for that since it either catches up with the hands that flat 3-bets OOP, or it leaves us with an easy fold. And since villain is OOP and his range is wide, we should have a super profitable 3-bet here.