My son and I are still new to the game. More often than not, he picks his team first and then I scrape together a team with the same number of points. Recently he has been playing a 400 pt team with 2 characters that are both tentpoles (see below). What sort of team and/or playing strategies can I use to combat such a team?

Lots of outwit and ranged characters

I can't use Outwit on Monstrous Body or Total Elimination of Super-Soldiers, correct? Because they are both 'abilities'?

But I can use Outwit on Brain Bolts and Rebuilding From The Rubble, right?

Correct on the outwit. You could also outwit improved movement ability via flight or willpower via indom.

You could also run some incapacitate in order to slow them down and if you are outwitting willpower then deal some pushing damage when adding the second token.

From recent sets..

Aou wasp for dual target incap
Hank pym for outwit and prob
Hercules for melee and tie up.
100 pts left for a good secondary attacker.
You'll out action them especially with the incap, 3 attackers herc has ss flurry and reduces damage by 3 to their two attackers and you have prob/outwit/tk that's not including what your final figure brings.

Horrible run on sentence I know.

Heck if you outwit defense on the big guy and flurry with a ultra heavy he's dead after. Easily set up with tk outwit and prob on pym

I have Hank Pym and Hercules, but not Wasp. But that gives me a starting point.

Thanks (to all) for the pointers.

What about using Gorilla Grodd (in lieu of Herc (220pt)?) for MC (without 150pt limit) and Flurry. Though his Flurry doesn't appear until much, much later on the dial. I assume I can MC anyone, including robots, right?

Grodd is good. You mc them both to attack each other then psychic blast Tess one. Can't PSB the other:-(. I was thinking herc at half dial. You only need the outwit then tk in to hit once for him to do work.

Banshee from deadpool
Agent 13 CaTws
Common malkith from TdW

These all turn off defense powerspowers passively. Outwit is probably the way to go theif you don't have them

Using various combinations of Outwit, Incap, Perplex, and Barrier will help keep his guys in check and your guys alive.

Remember too that Perplex can perplex down certain of his guys' values, such as speed or range, so that can help keep your guys out of his reach. Or attack values to help him miss your guys. I say that because it seems like newer players tend to think only of perplexing up their own defenses, when it is sometimes better to perplex down the other guy's attack values.

Here's an example:
Let's say you want to perplex up all three of your figures' defense. But you only have one Perplex. Instead of choosing which of your figures to boost, just perplex down the attack of the nearest threat. That has the same effect of perplexing up the defense on all three of your guys.

Also, as other have stated, don't forget that you can outwith their flight ability, Indomitable, and both Improved Movement and Improved Targeting.
The bolded part won't work because if you mind-control both of them, then they're friendly to each other and therefore can't attack each other. But you could move one to position for an attack by the other. That would work.