Just did Captain America and Wolverine.
Kill everyone you can find, and make sure you disarm all of the bombs as they give u a nice sum of bonus points. When fighting winter soldier, I had shield bash maxed out and just repeatedly spammed that move charged up on him. Once the clock hits 30 seconds, run round to all the consoles and keep hitting them until you have another minute on the clock, and return to killing winter soldier. Rinse and repeat and you should beat this with a gold easily.
I maxed out Claw slash because when wolverine is enraged (this is like momentum it's the staggered bar within the circle next to wolverine's health. He is enraged when this is flashing), claw slash is deadly to the boss if you can trap him in a corner. Farm the unlimited spawn chamber (taking out as many consoles as you like to make the crowd manageable) until there is around 10minutes left on the clock.
NB!!! Watch out when using Wolverine's extreme attack in the unlimited spawn chamber as you may accidentally destroy all the consoles which would stop the spawning.
For the boss, if you hear a clinking noise when you aren't attacking him, there are AIM troopers attacking the things you're supposed to be defending. Wipe out all of them before continuing to attack the boss as if you lose all 8 of the things (sorry can't remember what they are called), you fail the mission. Once there are no Aim troopers spam the boss with the stun combo and the occasional claw slash, (don't overuse claw slash as it is in your best interest to conserve your energy). One you become enraged, try and get the boss near a wall or corner and spam that claw slash as this does huge amounts of damage. It's hard to control the attack, so that's why it's best to do it up against a corner.
You will inevitably lose a couple those "things" (I lost 6!) but it shouldn't jeapordise your gold as long as you get enough kills in the unlimited spawn area.