I tried it in singleplayer once, and got a few comments for you.
- Some tooltips need more info: Basic Guard tower's crit just says you need the "Steelhead arrow" upgrade, but you need the 9th upgrade of it before they get crit. Also, it says they are weak come late game, whereas I found them to be really awesome once fully upgraded - for 10 gold each you can MASS them and put them just about everywhere.
Hippogriph archer doesn't tell you that it has a slowing attack (which was a good surprise, but would be good to know beforehand)
The Ancient Protecter has the Bash ability too, don't think that's stated in it's tooltip either.
- I think the Long range tower upgrade is expensive, I didn't manage to get them before like round ~14, and by then I had sold the few long range towers I had, but they are good once upgraded, just doesn't seem to be worth it imo.
- Poison towers are nice, especially because their slow stacks if a target is hit by two different towers - don't know if this is intended, but mobs slow down to just about no speed at all.
- Arcane towers being unable to hit infernals and the drakes was a bit annoying, but unless you only got arcane towers its not that bad, intended or not I dont know.
- I didn't get to try the hero sadly, but I bet she's much fun (I forgot about her because it took a lot of rounds before I ever had 1k spare gold, and by then I bought upgrades).
- I like the way you get wood, but it seemed like a problem to me at any time. I was always on top with wood, ending with about ~35 after buying the hero. I don't know if you run out later with more rounds though.
- Extended tooltips for the future maybe, displaying range (esp. this) and damage values, so people know if thats what they want, and they are sure they place them the right place.
- I bought one of the archers at some point, and it litteraly took me 10i'sh rounds before I ever found her. I know the tooltip says shes got blink and stuff, but I kept looking and looking for her, until I realised she's moving by foot and got stuck on the lil' platform, standing behind the "wood mushroom".
- Boss was cool, I liked the music addition - and almost had him killed, think he was down to about ~6k? I don't think I killed any of the Dreadlords that came sometimes in early rounds, but if I had played the map before I would probably have been able to do so, knowing about the towers and paths etc.
- Last, the terrain seems pretty big - the path thing they walk in is really big, but I suppose it's made for 8players and 2 each side, meaning it's not that big afterall.

Mobs do move pretty slowly through though, and if you miss one it can take a really long time before it moves to the end.
Fun map overall, but pretty slow because it's huge path/maze/dontknowwhatitscalled, it probably needs to be more fast paced if you want more rounds and to be playable online, don't think people have enough patience for 4 times as many rounds.
EDIT: Okay I saw its meant for 4 players, too big a map then imo, but it's easily doable to cover both your "lanes"/whatever anyway.