1. I certainly would not advocate using Feint with one Pokémon and Exploding with the other. If anything, Feint would be used for predicted Explosions from your opponent.
But your Feinter still dies from their Explosion then. And if their Exploder is faster and you are at low health, they may just opt to kill you without Explosion, meaning you wasted a turn and possibly a Pokemon you could have saved with Protect. Too situational.
2. You don't have to use Feint for multi-target attacks. If you really need to KO a specific opponent that you think might Protect, you can just Feint with one Pokémon and use a targeted attack with the other. If the Pokémon with Feint doesn't have much else to do during that round, I'd consider it a legitimate use.
But Feint takes up a moveslot, and again, it's just too situational. What if your pokemon DOES have something to do? What if the enemy is a Ghost type? What if the Non-Protecting pokemon won't be able to KO anything next turn? (Allowing you to attack the Protector next turn) What if the Pokemon doesn't use Protect and you could've just attacked? Too much uncertainty to make it worthy of a moveslot, imo, especially looking at the Pokemon that learn it.
3. I think you're right about this. But you can't sweep a team with Endure/Reversal in 2v2, either.
Depends on the setting. Reversal is meh, but things like Endure-Salac Groudon are capable of inflicting some serious damage vs. the right teams.
4. I agree with you here. Imprison does Feint's job better, and to both opponents to boot. The only caveat is that Feint has a priority modifier and Imprison doesn't. So, Feint can be used in emergency situations. Also, Imprison won't help against Detect, rare though it may be.
Your Imprisoner can actually use moves besides Feint, too. But when you get yourself in these "emergency situations", how do you know your Feinter will even be on the field? Too situational.
5. True. Ghosts are immune. Of course, in the Explosion case, Ghosts won't be using Protect anyway. You could use Foresight or Odor Sleuth instead, but that's another discussion.
Yup. Foresight is extremely underrated imo.
6. I have to completely disagree with this. Just as an example, consider this:
Hitmontop @ Intimidate
Fake Out
Feint
Mach Punch
Helping Hand
Voilà: a terrific support Pokémon. Intimidate and Fake Out help you set up any sort of hard-hitting partner. Helping Hand gives your partner's attacks extra punch and Feint makes sure that they hit through Protect and Detect when they need to. Mach Punch for STAB damage. The damaging attacks are all weak, but they allow you to completely eschew Speed. With all those extra EVs, you can make Hitmontop into quite the tank.
Something with 50 base HP (Despite its good defenses) cannot tank very well, especially in 2v2. And even if it had 100 base HP, what's to stop your opponents from bypassing Hitmontop and attacking your other pokemon? The moveset is fine, though a Helping Hand is a pretty bad 2v2 choice when you think of how much more damage you could be doing and how much more type coverage you could have if you just used another Pokemon that actually does damage. Oh, and Dusknoir outclasses this completely except for Fake Out and Intimidate. Which is unfortunate because really, this is as good as a Pokemon set trying to incorporate Feint will get.
Basically my point is that Feint is an alright move in itself, but it's just too situational to try to base sets around or let it take up a valuable moveslot. Even when the planets all align and you find yourself in a situation you need to use it and are able to, the result won't be as game-breaking as many would think.