Does Argent Ordnance Stack?

Argent Ordnance does not stack with Weapons of Light, High-Energy Fire, or other damage buffs. When you have Charged with Light stacks, a buffed named "Godslayer Warheads" will display on your screen. Damaging a target will remove a stack of Charged with Light after one second.

Does Argent ordnance stack with Weapons of light?

While Charged with Light, readying or firing a Rocket Launcher grants it increased damage and reload speed. Damaging a combatant with a rocket consumes one stack of Charged with Light.

Does high energy Fire stack with Rampage?

They do stack with weapon specific (rampage, kill clip, etc).