The main issue I personally have with the defending is how the AI is completely uncoordinated. Since it's AI this can hardly be avoided, but for example having the enemy spawn mostly in one area (including their armour assets most importantly) with a few infantry squads randomly attacking from different sides. A concentrated attack where the armour cannot be singled out so easily will probably prove more of a challenge than is the case now.
Thanks for the clarification.
Edit: I don't want to annoy you guys, but have you tried running the server with the -nolog parameter? From what I have read it's a good way to increase performance (at the cost of logs, ofc.).
I have seen a lot of CBA related errors on the server, although that is hardly related. With TMR the server seemed to function just as well as it does now.