I played every story level on "Hard" mode but still found the boss battles to be easy. It's hard to evaluate this because it was the Beta and it lacked bosses. I like how Bungie gives you the option to change the difficulty prior to your mission. However, judging by what bosses were available in the Beta they were too easy and did not need any strategic planning for a victory. Bungie mentions they will provide content and support for this game for months and even decades for those hardcore fans. However, I've seen no reason to repeat boss fights. They were non-rewarding, anticlimactic, followed by a countdown to be warp back to your ship. There was no carrot enticing for me to repeat this. Defiance, Borderlands they teased you with a possibility of rare rewards/gear/loot and offered well designed challenging boss battles that were fun and challenging to rinse and repeat. This was not evident in Destiny which concerns me for longevity as a PvE'er. Grouping in PvE. Lastly I want a reason for me and my friends to max out all the available classes and why party selection should play a role in instances. Do we run a Titan, Warlock Hunter, or a Titan, Titan and Hunter ,etc. We were limited on the full potential of each class but by the beta all classes felt the same Honestly, this question is premature because it's basing the bosses on a very limited exposure to what bosses are available in the Beta. It would be like comparing Knuckle Dragger (1st boss in borderlands 2) to your invincible bosses in Borderlands i.e Pyro Pete, Hyperius. Bungie teased high tier instances for level 28 and higher. I'm excited for this but my original concerns still looms. I'm optimistic and really looking forward to this game, I hope it delivers the challenge and rewards for PvE i'm looking for and hopefully they include some hidden/secret boss fights as well.