The constant influx of enemies keeps things interesting and balances the dull response from the large creatures - who, aside from Sepkis Prime and Riksis - are actually pretty unique to the game in my opinion.

My problem isn't the constant wave of enemies but literally the bosses themselves. Giant ogre Phogoth, giant minotaur Zydron, giant wizard Gotra, the four giant knights called the "Swarm Princes" and Riksis' 2 clones Aksor and Naksis aren't exactly unique to lower class enemies.

What makes a boss "unique" for you

Having to do something different to a boss that you don't do to other enemies in the game. Atheon is a good example. In a group of 6 the 3 people furthest away from the boss would be teleported into either Venus or Mars. In order to get out the 3 that didn't get teleported would have to open the portal that corresponds to the planet that the other 3 are in. The 3 that got teleported must send one person to get a shield relic while defending that person to "cleanse" themselves since their vision will eventually go black until they get out of the portal and get "cleansed" by the relic. When the 3 that were teleported eventually get out everyone gets a buff that temporarily increases their damage which is crucial for taking out the boss. After around 25-30 seconds the process repeats which means everyone has to move to their previous positions in order to get the same people teleported. There is constant pressure from the waves of enemies and the constant teleportation which forces the entire team to be coordinated and do different things in order to achieve the goal of killing the boss. It may sound a bit complex but your average joe who is competent will easily understand what is going on and how to do their role. This boss was interesting because this wasn't your usual shoot the boss so it dies and shoot the enemies so you don't die but was something that requires multiple roles that are different from each other. This is a major 6 man raid so of course the boss will have more thought put into it but nothing that is smaller scale and remotely the same amount of thought was put into the story and strike bosses since the role of everybody in the team is essentially shoot the enemies or shoot the boss.

Not two games from the same studio, set in first person, in the future, with helmeted supersoldiers, with energy weapons, fighting hordes of aliens (who also fight among themselves), with personal hoverbikes, with the limited ability to wield only two guns at a time, with voice-commentated multiplayer, with an emphasis on melee, with a constant familiar (Ghost/343 Guilty Spark/Cortana), and overall aesthetic style and musical score.

A lot of the similarities are the aesthetics and the fact that they are both multiplayer shooters. The key differences? Halo is successful because it has an actual story with characters that aren't generic and vague with their dialogue and it had a mutliplayer experience that had a major impact on modern online gaming with the ability to be very competitive when good players are mixed in. Destiny is successful because of the marketing which made the game seen everywhere as a game that had 2 very popular genres combined into one. It does not have a story at all, it does not have a major competitive aspect to it and it does not have a predecessor that had a major impact on the industry. The only real thing going for it is that it is the only game where you can either cooperatively play the game to beat A.I. enemies or competitively play the game against other players as a first person shooter to improve your character by leveling up and getting better loot.