M8n has been more forgiving in duty finder for me than M4n for instance. I recently was bored enough to farm out a 2nd relic so I was doing M4n a bunch for the "precision" parts and I found success rate on that was far lower in duty finder than m8n. Granted, both usually succeed.

It seems there are really only 2 things that prevent duty finder groups from muddling through a instance (imho):
1) How tight is the dps check?
Dps, while not normally important in most content, when it's important it's make or break. If there is some enrage and you have people making mistakes laying dead on the floor, it's hard to recover. I'd put healing or tanking above that normally but if we are talking about easier content (as in normal mode or tome farm stuff), generally most tanks or healers are fine if the other one is less experienced/skilled and dies (and many pride themselves on the challenge of doing it 'solo' so maybe they actually want to see what happens if their counterpart dies? 0.o).

2)Is there a instant kill everyone (wipe) mechanic that as few as one or two people could mess up?
Personal accountability is a important thing of course, but most people don't seem to care about getting themselves killed in duty finder content and often blame it away on something else ("I didn't get healed!","I lagged!","Tanks, why u no aggro!","Why did I die, I did it right!"), and maybe it's fine because they can get rezzed or whatever and no one really cares that much. However, if they can kill the entire party simultaneously by their mistake then you probably aren't going to clear it unless they decide to own up to it and change (which isn't probably going to happen with strangers that will never see each other again after the group is over).

But as far as a8n, it's very forgiving. I've farmed it lots with strangers and I think I've only seen the enrage once (I think it was just me and 2 others standing for a long time). My reaction to that was: "This has an enrage? 0.o"