Most raids in D2 with the exception of Leviathan do have multiple defender/add clear/floater positions all of which are easily definable in their role and require little team work and only some communication between key roles. These mechanics are divided among teams of 2-3-4 so knowledge of the entire battle or even all of the mechanics isn't even really necessary since those mechanics are subdivided among many people working cooperatively and coordinated. Crota was a glorified strike and people are forgetting how long it took people to beat VOG when it first released. Granted it was destinys first raid, it was definitely challenging and cheesing and glitching has been rampant in this game since day one due to peoples inability to deal with complex mechanics.