[Phanx]

The function only processes buffs because it only includes code to process buffs. If you do not pass a filter, UnitAura defaults to looking at buffs. If you want to look at both buffs and debuffs you need to do two loops -- one for buffs, one for debuffs.

	-- Buffs:
	for i = 1, 40 do
		local name, _, icon, _, dtype, duration, _, _, _, _, id, _, isBossDebuff = UnitAura(unit, i)
		if not name then break end -- no more buffs on this unit
		local priority = list.raidAuras and list.raidAuras[name]
	   	if priority and priority > bestPriority then
			bestPriority = priority
			bestIcon, bestType = icon, dtype
		end
	end
	-- Debuffs:
	for i = 1, 40 do
		local name, _, icon, _, dtype, duration, _, _, _, _, id, _, isBossDebuff = UnitAura(unit, i, "HARMFUL")
		if not name then break end -- no more debuffs on this unit
		local priority = (list.dispel and list.dispel[dtype]) and 5 or (list.raidAuras and list.raidAuras[name])
	   	if priority and priority > bestPriority then
			bestPriority = priority
			bestIcon, bestType = icon, dtype
		end
	end

(Also, I never saw your question, because you just edited your post, and that doesn't flag the thread as unread. Generally if it's been more than 5-10 minutes and your original post didn't including anything that requires a reply, you should just add another post.)