I previously let my feeling known in regards to the upgrade from Militia to Footman Tower could use slightly more attack power
Here are other upgrades I feel should be bumped a little to make them compatible,
Ranger Tower Wrath of Forest - Currently upgrades 2 and 3 only increase the length that Wrath of the Forest Holds enemies, which also effects total damage (1 second 80 damage, 2 Seconds 120 damage, 3 seconds 160 damage) - I typically hardly ever use this upgrade I try to but finding situations I feel it's worth it are rare. Possible upgrades include reducing reload time by 1 second on the 2nd and 3rd upgrade, or increase damage per second by 10 each on the 2nd or 3rd upgrade. By comparison, the Big Bertha Dragon Launcher's upgrades also only increase damage by 40 each time, but it only cost 75 for each additional upgrade
Berserker Tower 2 axes and Nets - Cost 300 to increase berserkers attack by 10 on the initial level, level 2 and 3 only cost 100 but still only increase damage by 10. I hardly ever find this upgrade worth it. Suggestions are to decrease initial cost to 200, and/or increase the attack boost by 5-10 for each level gained. I mean they have low Armor, and by the time you get them your facing waves and waves of armored enemies that can kill them fairly quickly, they should at least be best offensive ground troop. Right now they're outclassed by the "Sirs" since they're Holy Strike does high damage and AOE and have much better armor.
As for Nets I hardly ever use Nets, Flying enemies are usually taken care of by a mix of Ranger Tower with poison and Big Bertha Dragon Breath missiles and assorted magic towers of course. The biggest reason I hardly ever use nets was that they don't slow down ground units either, They should be able to at least throw nets at small targets, or the Nets should be able to do damage, or take away a flying enemies flying ability and bring it down to the ground for some Axe action. I don't know if nets do the last one already since its been so long since I used them.
Tesla Tower everything
Its just in short inferior to Big Bertha, BB has a wide range due to Dragon Breath missiles. Cluster bombs (which are handy although I feel they could use a small damage increase in upgrades 2 and 3), and it just packs more Raw power. There are a couple of things you can do to improve the Tesla Tower. You could increase its Attack speed from Very Slow, to just Slow. Which would also help with Overcharge, and/or you can make its "lightning" ignore Armor, which will also help with Supercharged Bolt, If you do both I'd recomment slightly lowering its Lightning Damage
Really the only level I've used Tesla Tower effectively is one of the Ruins of Acoroths Challenge that was mostly wulves and other mass low hp units