If the interceptors weren't useless, fighting the tank in the valus ta'auric strike with interceptors would be fun. Oh how about an enemy that actually chases/ hunts you down instead of standing in place or moving in a line. Like the person getting aggroed has a warning so that they have a chance to run and hide before they get rushed. Environment effects would also be cool like luring a boss to a trap of some sort. Or maybe a boss that can only be killed by pushing off the map since we seem to like that strategy. Or opposite boss fight, we are forced into a confined space and have to fend off hordes and hordes and hordes of little creatures all attacking at once. I'm thinking thralls here but shanks would be hilarious. Or a boss fight where killing the boss isn't the hard part but escaping afterwards as minions try to avenge their leader. Basically there are so many different styles of boss out there besides stationary bullet sponge with splash attacks and bungie could definitely improve by experimenting a little more with strike encounters.

Every boss fight in the excessively japanese lost planet 2. Those were fun. They were sponges yes but you had multiple avenues to speed up killing them be it use the vehicles or the environment to kill the bosses

I liked almost all of the Borderlands (1 and 2) fights. Warrior in Borderlands 2 was pretty slick with all the environmental hazards. Half-life holds a special place in my heart for obscenely hard end - bosses with (at the time) incredible locations to fight in. Halo's final boss fight where you explode the ship is a favorite because it wasn't a boss but a challenge to work fast under high pressure.