I think you have a wrong perspective when facing stax with control decks. What you say is an effective play if we were playing storm combo, but playing control decks using only massive bounce spells helps, but does not win. Eot hurkyl's, ok. In your turn you will untap, draw and pass the turn 80% of the time, and the other 20% you will combo out. And if you pass the turn, they will just replay their entire hand again. Maybe you will counter one or two threats, ok, but the rest?
Against stax, the best plan is aggro mode. Why do decks like goblins or RG have a very favorable matchup against workshops? Because of their quick clock. A quick and cheap clock is the best solution against any kind of lock. If you drop a 4/5 goyf onto the table, they simply have to find an answer to a 5 turn clock, or they are out, even with their crucible/strip mine lock, or with their 4 spheres, or whatever they dropped onto the table. Even a smokestack can be useless if it does not hit the table soon. And the difference between RG and our deck is that we run counters to avoid their few responses to our beaters.
Exactly the same way as MD Gifts did it.
I think any tezzeret build is far away from MD gifts deck in almost every aspect. MD gifts run almost every card as a 4x of, and that way its playlines were easy to follow and almost the same. It resolved eot a hurkyl's, then a gifts and just won. We run almost every card as a singleton (except for countermagic) and that way we have tons of different ways to develop our play. And we not run any single card that just "wins" the game, we need at least a combination of two, which is much harder to assemble. Don not forget, MD gifts was a sort of storm combo deck. We do not run tendrils of agony to win the game, so we can't focus the matchup the same way.
Apart from all this, I can't see why energy flux isn't an autowin. It clears their board completely. And we lose 1 or maybe 2 moxen, ok, what a problem... I always win the match it hits the table, seriously. Its only problem is the cmc 3 it has, that makes it sometimes hard to resolve through several spheres, but being blue and running at least 3 basics I think there isn't a better solution without running red, anyway never more than 2 copies, for sure. Trygon predator was simply crap, and engineered explosives is a good sideboard card in general, but I wanted to end the game better than just hit their spheres