Hey GriffonDefender,
My friend and I just playtested this on Battle.net. I actually have to say, I was surprised at how fun it was, given how simple it still is at this point.
Some suggestions:
1) Make splash from towers not affect allies. Our main base actually got killed by an Ultimate Defender Tower auto attacking enemies. In addition, most of my stuff got wtfpwned by my ally's Flame Towers early on.
2) Make your Towers bulkier, and make a Repair option (Repairmen, or Repair on the workers). This was a big problem for us. Towers were a very limited investment seeing as they only lasted 1-2 waves each. We ended up just getting every hero, and then experimenting with the Ultimate Defender Towers (which ended up killing our base on Wave 9).
3) Make Mana regenerate at the end of waves, like you do with HP. The HP regen option from base inbetween waves was great, but we needed Mana to go with it.
4) Fix the Phoenix hero's Phoenix Form. It's completely glitched. The first time I used it, I meta'd into a hero with no inventory and had to re-learn my abilities. The second time I used it, I turned into a Phoenix with no inventory and no abilities. When I un-meta'd, I was back at level 1, and had to re-learn all my abilities.
5) Give us towers to start off with, owned by a computer player. It would make the measly 60 second Grace Period a lot more manageable. Optionally extend the Grace Period.
6) You could use multiple Computer slots for your various unit spawns to reduce mass unit lag. Right now it's very visible and affects gameplay.
7) Expand on the existing tower builders, giving them more options. Right now there are only, I believe, 6 towers in the game. I'd love to see more!
Overall, this is a very good start to a game. Honestly, I think the reason you're getting rejections is because you are posting games too early in their development. I checked out a few of your other maps, and they seem to still be in the alpha-beta range. Why not wait until you have a completely functional, playable game? If you did that and followed the Hive's (rather anal) rules about crediting and making good descriptions, I'm sure your maps would get approved.
You are actually quite a decent game designer. I wouldn't give up, if I were you, I can assure you that it wasn't a waste of time playing your map.
Also, don't take map rejections personally; I know it's easy to, but just try to take criticisms in stride and improve upon the areas where your maps are weakest.
Anyway, good luck!
- Mech