I enjoy playing as zagara. You can only max on 100 supply, but you get infinite larvae, cheap units and tons of banelings for free.
However, I don't think co op will stand the test of time at all. Im level 10 as zagara and I feel like missions on brutal are now unloseable, even if my ally doesn't do much. I shudder to think how easy it will be at level 15. Getting to level 15 is a pretty long task given how tedious/repetitive the missions are, I doubt many will do it on all commanders. They should either ramp up the difficulty of brutal even further so you're forced to work as a team or lose, OR add another difficulty above it.
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