Threadnought! So...your both arguing for roughly the same thing? Which is similar to what everyone else has said: Hard-modes are a cheap way out. We want more content not the same thing with moar health to grind through! Why not give each boss a certain gimmic? Say a mechanical boss with an enrage timer. The boss starts off blue coloured, but slowly turns red as the fight progresses. When he gets really close to his enrage, steam boils off him and glowing cracks appear in his armour. However... there is a useable object in the room that, if the raid kite him over to it, they can activate to spray him with water, cooling him down (adding a few minutes onto the timer, and possibly stunning him for a second or two). If you can kill him without using the shower, you get extra loot (HC level) and achievements!