A lot of people will agree, skeleton level 4-5 and witch combo early game is impossible to defend. Imagine, you have almost no towers. And then 1 person or more will rush skeleton horses level 4 and witches (both immume to mage). There is NO way you can stop it. Its too cheap and too easy to unlock and upgrade with xp. So my suggestion is: Make skeletons and witches cost more xp to unlock and upgrade. It will let both teams have more time to make a better defence and unlock potions. So the game can be more enjoyable.
Another thing, every tower should have an instant upgrade to the last level in my opinion. If you have a lot of gold and you want to upgrade towers it takes too long to do so. An instant upgrade will make it more quicker and it will be more enjoyable to play tower defence.
Another thing, every tower should have an instant upgrade to the last level in my opinion. If you have a lot of gold and you want to upgrade towers it takes too long to do so. An instant upgrade will make it more quicker and it will be more enjoyable to play tower defence.