Hey, I'm one of the testers who played with mech_warrior and I'll leave my thoughts below,
Overall I find that rocket tower dominates land enemies most of the game, and if your smart with your resources you can gradually get anti air and saving boxes as you need them. Also, I generally get level 2 ice for most of the game. Either a glaive or a cannon tower is good as an extra to help prevent leaks on those boss rounds, but overall I find most of my money is going into my rocket tower.
Destruction towers are good late game, but only to block off your spawn with. Ideally you want one maxed ice, one maxed destruction, and one maxed anti air on the cornerspot of your spawn late game, while you max golden beam towers for the 3x crit for the boss in the middle. If you max destruction towers you are inevitably going to screw yourself, and beam towers are far cheaper, and have 3x crit compared to destructions 2x crit.
Saving towers are a huge help in the game. I think I had 8 of them In the game where we beat the boss since they have a nice rate of return. I think these are fine, since we only barely beat the boss, even with my income.
Lotterys are useless. There is little point to building one besides getting the medal. Any decent rate of return from that is far too rare to try for, and if it were any easier it'd probably end up breaking the game. I would honestly scrap the tower, but since the medal is already in you can keep it if you want.
Overall, I think this is a fun game and the balance isn't that bad. Instead of giving creeps armor like the one guy suggested (It's not a neccessity in tds), I'd suggest working on balancing out the other towers more. I think the rocket tower is far better against land than any other tower.
Keep up the good work, and I hope to see you improve this as best ya can!