It would be a good idea to make inventory effect to defensive buildings and waves. So this will make defences and inventory more interesting and various.
Merc boost perk makes ninjas in defence stronger.
Insta troop Cooldown will decrease the time to defeat a base but that shouldnt be more than 10 second.
Piercing, fire, poison etc. shields will give 5-10% of resistant for buildings.
For troops and pals
Troop damage and health bonus perks will increase the health and attack power of selected troops in waves.
Gargoule bonuses effects both gargoules and gargoules tower.
Special pal perks increase special ability bonus of the selected beast.
Pal flute increases the healt of the beast
Pal damage perk will increase pals primary attacks
Hammerstrike damage perk makes skull tower’s attack power
Toxic cloud for snake tower
firestorm for firebolt tower
swordrain for spikes and arrow tower
heal for heal tower
blizzard for frost tower
shield perk for basilisk
swordstorm for barricades and blockades
sonic blast for bomb tower
black magic for lightening tower
I dont know how auros or general perks effect on defence. They may be prepared for castle buildings like tawerns, blacksmith, castle gate etc.