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Just played it a few minutes ago. The middle hill ref'd in the title is useless. The SPMAs don't do jack... and the same for the node. I would recommend at the very least changing the SPMAs out for something more powerful.

You do know you can kill 4 nodes from one spot with the Helios Artillery? Two shots kill a fully charged node (and one shot kills most of the vehicles and infantry). And with a slight movement you can basically hit the other two.
I agree though the other artillery pieces aren't so useful. I wonder if changing as you suggested maybe a more powerful tank - maybe Hurricane, Hydra, Heavy Tank or similar as a reward.