Is hero cooperation worth the cost?

Hero cooperation will let you add a second hero to the APC's formation, this will give you the option to add many more troops and then also unlock and use the heroes skills to make the APC stronger.

Whether this is a priority for you at your current stage of progress is up to you. You may have other upgrades and research that you want to get done first. But it will help and it will let you then move on to further research for that APC to improve it further.

Yes, definitely! You won’t stand a chance with only one hero in your apc’s. You might not want it yet, but you will. The third hero is also important.