Without The Enclave?
I'll edit in my thoughts later I'm too tired right now.

O_0*

Yes I think so

Could well be. Though, better implemented one timer in Fallout 2 would be more preferable.

But definitely dropped as a faction in Fallout 3.

Not necessarily. The Enclave has not been well used overall but there's potential there. For instance I thought the New Vegas handling of the Enclave was well done and surprisingly poignant when you consider the monstrous goals and shallow presentation of the Enclave in Fallout 2. That is the Enclave's place in Fallout now just as the Unity transitioned into the story of what the remnants of the Unity did after that had been taken away from them.

What did not need to be done with them was the Fallout 3 (and to a lesser extent Van Buren) approach of having Enclave splinter groups and organized units and outposts all over the damn place. They certainly should never have been the villains in another Fallout game.

It's not the Enclave that's at fault but rather how they are placed throughout the games. Redundancy would describe them well considering you wipe them out in nearly every game only for them to come back full force in the next one. The only thing that makes sense are remnants and very small groups. By the year 2300, if the Enclave still holds power there's a lot of explaining to be done on the writers' part.