Do troops in the garrisons come into play when enemies get close to the tower?
No the troops do not come out of the towers when you are attacked. they basically provide buffs to the towers based on their level. I did notice that the more skilled up a Hero is, the more of a buff they provide.
I would like to point out a variance to this. I have x3 lvl 60's at base level, not upgraded.
When set to a tower here is the results:
Ninja gives 150 points
Champion gives 150 points
Minotaur Chieftain only gives 96 points
What's the issue?