there seems to be zero strategy at all other than rotating aggro during bosses
The subclasses for each class offer a different approach (generally, the default being the offensively based subclass, while the one attained after level 15 is more defensive/buff specific.
Which grenades you use, how you use them, how you let your attributes stack to loop your abilities, reviving each other when downed, etc. can change the entire course of a strike or raid. Try jumping into a strike with no friends and let matchmaking set you up. You'll fail at least once, if not more, because you don't know what to expect from each other nor are you set up to take into account what they do well/don't do well (unless you are massively over-leveled and don't use the difficulty modifier).