I need help building a 600 pt golden age team. The scenario is 600 pts, golden age, and every turn, choose a friendly character and make an attack roll against them with an attack value of 11 and a damage value of 4. This is supposed to replicate the world being destroyed

If you wanted to use the scenario against your opponent you could use something like:

SLOSH Bizarro (75 points) + Guard of the Citadel + 2 cheap barrier figures (R Avalanche?)

You can also pick any naturally high defensive number (printed 20 isn't hard to get in golden), that you don't have to use extra perplexes etc to waste the scenario attack on.

Once you pick a method of either utilizing or attempting to ignore the scenario you can just build as you normally would. As a final option you can pick characters that flat out don't care that they got hit for 4 (several 600 point colossal characters come to mind).

Personally I would use one of the above tactics against the scenario, or play a supremely aggressive strategy and a few 1/2 point pogs to buy turns (I self impose highlander, otherwise lian harper horde just lets you ignore the free attacks, but leaves you open to Ziran if anyone brings him).

I say, use lots of horde tokens. Horde tokens are like bizarro, but better (and you can use more)

Let me suggest:

Skadi's Warbot 30 (not stackable, but a great pog)
Warbot (machine gun) 15 (pulsewaver) (7 allowed in a stack for 105pts)
warbot (rocket) 15 (not a pulsewaver, but at least +2 to attack and damage values)(7 in a stack)
Mud Golem 20 (when stacked, penetrating poison)(4 in a stack)
Asgardian Warrior 18 (6 in a stack) (amazing with FI Odin)

Theres a lot more horde tokens in LOTR sets too, but not able to look those up at moment

I was thinking maybe using a headpool and Donald Blake. Headpool only takes 1 damage, and Donald Blake heals em up.

Lol, that's funny. I like it and is less than 60pts freeing up plenty of space for bigger and better things.