We've ran a Dynamis-Bastok with about 8 people, all of them were either mules, second characters, or borrowed characters. With at least two of those people two-boxing, and a few playing as jobs they never played at 75 in that type of a situation. We were still able to clear a large portion of the pre-boss mobs and get all time extensions on just our second attempt, and iirc we got 4-5 ores? Our luck on drops for that run was rather shitty overall.
This is with characters that had mostly sketchy gear and merits, and there were definitely some avoidable time-costing mistakes made that could've been avoided (as to be expected on only the second try with mules!). I'm rather certain a strong group of 6-8 people could do just as well if not much better with smart pulling and everyone playing their job to the fullest. Especially once you perfect a rhythm and strategy.
I'd actually really like to try this with a decked group of 6 to 8.