Let's say I use the Greatweapon Master ability ( -5 attack roll for +10 damage ), could I also combine it with a War Channel Divinity ( Guided strike + 10 on attack roll ) Are we limited to 1 option per attack action ??
blip wrote:
Yeah, I didnt see anything about stacking at all in the rules.
The combo you mentioned should be a staple of the War Cleric.
IMO, Greatweapon Mastery should be used whenever you have advantage, 2 rolls is about the same as one roll with a +5, so in the long run it should be +10 to dmg without penalty if you use it with advantage.
This reminds me of true strike and Power Attack from 3E. 
In general, the "advantage = +5 to hit" rule is a good fallback, but keep in mind that advantage and -5 to hit may shake out differently depending on the target's AC and how much bonus damage your character deals already.