damage vs attack?

[sethmage]

Can somebody explain how the damage is calculated vs attack?
Example:
2 suspects: warrior 30 attack, and mage 10
Then we have a unit with base attack 20 and damage; let’s say 5-8 physical
So in the info window for that troop we can see 50 (20) for unit belonging to warrior, and 30 (20) to mage. How much damage that units can do respectively?

Reason I ask is during the famous spider fight with 3 trolls (1-1-1) they get over 200 in attack yet their damage is nothing to write home about it. Unless is so insignificant to notice.

I read something about a cap attack, but then if that’s the case what's good frenzy for? The attack is piling up but the damage stays the same?