Tower damage + Champion Defense

I am trying to work out how turret damage is affected by armour, skills and masteries.

Here is the information for turret damage as far as I am aware:

Turret        Range  Base HP    AD     Gains 6 AD every:        AD Caps at:
-----------------------------------------------------------------------------
Outer Tower   1000*  Various    152    1 min at each :40 second mark.   200
Middle Tower  1000*  Various    197    1 min starting at 7:00 mark.     263
Inner Tower   1000*  Various    210    1 min starting at 16:00 mark.    330
Nexus Tower   1000*  Various    115    1 min at each :40 second mark.   343
Nexus Obelisk 1000*    9999*    999    N/A                              N/A

• Does armour reduce it, the same it would for auto attacks?
• Do items like thornmail and skills like Rammus' curl reflect damage?
• Do skills like Maoki's ultimate (-15% damage in the aoe) or Alistair's ultimate (-75% damage on self) affect the turret damage?
• Does the last defensive mastery negate 4% of the damage?

Solution 1:

Lets break this out piece by piece.

• Does armour reduce it, the same it would for auto attacks?

Armor does in fact reduce the damage you take from normal towers. The base tower however deals true damage.

• Do items like thornmail and skills like Rammus' curl reflect damage?

Simple answer: No. Most abilities do not deal damage to towers either. Exceptions include Heimerdinger's turrets and Alistar's passive.

• Do skills like Maoki's ultimate (-15% damage in the aoe) or Alistair's ultimate (-75% damage on self) affect the turret damage?

Maoki's ultimate does not reduce damage taken from turrets but Alistar's ultimate does.

• Does the last defensive mastery negate 4% of the damage?

I believe so for the following reasons. It says it reduces "All damage" doesnt exclude towers specifically (the way Maoki's ultimate description does).

Hope that helps.