Agreed. A cheese is using something outside it's intended function. For example, using Solar Grenades to push Atheon off the edge. This is definitely a cheese as SGs are meant for damage, not taking up room so the boss has nowhere to stand. An exploit is where you do something game breaking to your advantage. The very best example of this is the Crota-Ethernet exploit. It's well outside the scope of the encounter and against the spirit of the game. The Cluster strategy is a tactic. It's a very simple raw damage, brute force method to deal with the boss as quickly as possible. Everything involved in this tactic is being used correctly and to it's fullest capacity.