Q:
Rata Sum Rune set
The radationfield used by the rune is different then the skill radiation field. The wiki just links there to give you an impression what it does cause the exact stats are unknown. Runes and Rune effects are never part of a combo.
Arise, ye farmers of all nations
Arise, opressed of Tyria!
Arise, opressed of Tyria!
IMO it’s useful for it to not combo because it drops on water fields when you want to use the healing combo effect. It would otherwise over lap and interfere, but it helps that it does not do that.
Finishers always use the oldest field, so if it drops on water, then you will still use water. The only exception is fire field – for some reason it always has priority.