I noticed it's a completely mixed bag. Sometimes people welcome advice, sometimes they completely ignore you as though you're talking to someone else (must be the OTHER tank in the 4 man they're telling to use flash), and other times they act indignant and will curse you out for a kindly put suggestion. I think it's best not to talk about gear, so I only stick to gameplay advice. A lot of the time you'll get a thank you, but if they go the ignore route, I'll usually repeat myself once more then just deal with it as it comes. If they get mad for you suggesting maybe they could use an aoe attack when you're pulling 12 mobs instead of single attacking because single attacking is much faster and more efficient, then I suggest just shutting up and once more just dealing with it, because there's no possible way they're going to listen to you if that sets them off.