Round out this first-time team?

Legacy is never a bad choice for rounding out playing this game the first time with others as he makes them the rest of the team better and my secondary one would be Tempest since they have a lot of versatility 

Both good choices.  Ra is a good one, as well, as he's pretty straightforward and very thematic.

You can almost never go wrong adding Legacy to a team.  He works especially well with Fanatic and Tachyon, since they have lots of low-damage attacks.

Completionist Guise, and in the MMFFCC versus Wager Master! (No, don't do that, please.)

I agree with everyone else that Legacy is your best bet.  Also make sure that it is against Baron Blade in Insula Primalis, as that is the intended first scenario.

I would agree with Legacy.  I don't like playing him that much, but having him around usually makes the game more fun for everyone else.

Do you know who you'll be fighting?  If the villain has damage reduction, the Tachyon and Fanatic players might get frustrated without someone like Legacy to boost their damage.

I'll also add that Christopher has said several times that Insula Primalis is the best environment for the first time playing the game.

Hey, if Wraith calls to you, she's still a fantastic choice.  Legacy is the king of synergy, but Wraith is strong in her own right.

You really can't go wrong in terms of combinations with the base set as long as you have at least one hero that can get rid of Ongoings (which all three of the previous choices can, as can Wraith) (Not to say you can't win with a team of Legacy, Ra, and Bunker, and Haka, just can paint yourself into some nasty situations that you wouldn't want to deal with on a first game).

Just a note, be careful of a new person with the Visionary as things like Precognition can really slow the game down as they need to learn the villain cards as well. Similarly, she can feel passive compared against more damage dealing heroes.

I’d also recommend Legacy as he makes everyone else better but is hard to overshadow with. The Wraith, by contrast, can easily overshadow them, or seem to. It’s hard to compete with 8 damage a round when you’re doing 1 or 2. Which is why he’s recommended for demoing with.

This team has great destruction, lots of ping damage, fantastic card draw and deck control and a few big shots of damage if needed.

That's a really solid team already.

Legacy honestly makes you the "LOL watch villain die so hard" team with boosts to all that ping damage and even more villain control.  I'd honestly go with Bunker over Legacy.  You don't really need more damage or prevention or villain manipulation.  What you need is steady damage and cards to sacrifice if limited destruction comes up.

You might be asking the wrong people. Experienced players rarely have anyone incapped (my wife doesn't even consider us to have won if someone goes down) except in the hardest scenarios. The stats project (link in my sig) has data on how often each hero is incapped, but that includes losses. I could figure out the exact answer but it would take time.

Depends on the villain, hero and environment combinations. But usually you can do it without too much trouble. Some heroes encourage a reckless playstyle which makes them more likely to go down (AZ, Fanatic, for example) but they also tend to have abilities in their deck to mitigate it.

The harder the villain, the less likely it is, but even against 4 difficulty you can win without losing anytone if you're careful and a bit lucky.

I rarely get heroes incap, and when I do it usually due to poor luck or me trying something tricky. It not the end of the world, there is some synergy with Hero incaps. I have had games where one hero was incap but everyone else was above 20.

My favorite wins is when there is only one hero up and about to lose but with everyone's incap you manage to pull a win.

I hope you keep enjoying this game and welcome to the community.