It's a very niche card, and I see it in decks where it doesn't belong. You really need to consider what cards you are going to play with the three resources you could (possibly) get from Band Together, as opposed to Power of Leadership. It's not always the best for setup cards because you want to play those early before loading up on allies. It's not great to play allies because you can only have 3 out at once, meaning this can only give you 2 resources for an ally (barring Triskelion and other shenanigans). It's probably best for events you want to play late in the game (like attacks), or something like Avengers Assemble!, that want you to have a bunch of allies in play.

This is one of only a few cards that can make your hero the defender of an attack aimed at an ally without exhausting your hero. Seems like a solid way yo leverage your beefy 13 Hit points as well as healing with Altman Residence!

Hidden Base is a highly efficient tough status dispenser. We usually pay 2 ER for a single tough status, so 3 ER for three is tremendous. Moreover, the stocks on tough have continued to rise with the prevalence of steady/stalwart villains and scenarios that punish ally blocking. It takes several turns of flipping to access the value of all three tough statuses, and you risk effects that ping you for one or two damage that waste the tough before it can stop a full villain attack, but these problems can be alleviated with Ready for a Fights. Hidden Base is obviously great with Colossus, who can now consistently start with two tough statuses every time he goes to hero form. Some perfect defense strategies might find the tough statuses awkward, but I think Hidden Base is an automatic inclusion in base-ically (haha) every Protection deck.

As a Basic ally, Yellow Jacket can work in so many different archetypes and aspects.

Also, a key ally for any upgrade heavy hero: Black Panther, Iron Man, War Machine. Also great for Repurpose Protection deck builds. Preparation cards are usually upgrades, so Black Widow and Nick Fury Justice decks want him.

I want to get this in to a Cyclops deck. It can only be played by Avengers. So either another player makes him an Honorary Avenger or Call for Backup gets around the restriction. Then Rapid Response recursion to keep him popping back in to grab Tactic upgrades.

Question, after you see the 3 encounter cards and pick one to tuck, what do you do with the other two cards? Those go back to the encounter deck or to the discard pile?

That aside is also a good card to deal with inconvenient cards, like a nasty treachery regardless of the amount of boost icons.