Since we want to balance towers more, making more towers maybe even vital, I had an idea.
What about Combo Towers?
Like f.e. Hansel and Gretel with Knusperhexe, a triple Combo, and each one grants certain abilities.
Hansel grants Gretel a Speed Bonus like 50% of his SPD adds to her, Gretel increases his Crit Chance 50% of her to his, while Knusperhexes attack SPD and chance to eat Children is raised by 50% if all three are on the Field
Full Moon, a Tower that doesnt need to be fed.
His Attributes could raise with the waves, like 0,5 or 1% each round you finish (dunno bout the balances), and as Combo it raises the STR, Crit% and CritDMG of all Wolves on the Field.
While more Wolves on the field stack Full Moon's Range (could be a 9 range tower with 8 wolves, maybe).
Kali a Tower that could Combo with Ganesha, while she (yeah, Kali IS female) absorbs half XP that Towers in range of 3 of Ganesha gain, pumping herself, and getting a slight Attribute Bonus for each XP drained. Ganeshas XP Bonus could be boosted, if Kali is on the field.
I know this hasnt been implemented yet, but it still hasnt been denied, so I came with another card, more detailled.
Hurley, the baby pug
Black Widow's cute baby pug
Base Str 1-1 (always)
Every 10 seconds a creep is forced to cuddle Hurley, slowed down by 50% for 5s, increasing Hurleys dmg by 1,5%.
Hurley has a 1% chance to instant kill creeps that arent immune (challenges, horseman), if a creep is killed in that way, Hurleys SPD and CritDMG are increased by 0,05%.
'Hey, little boy'
If Hurley is next to Black Widow, her potions affect him too and her Seductive Abilities are doubled.
Wow... The existence of XP-support tower is very valuable... +1 for Kali-Ganesha combo :D