I'm a Whm too and I think the main difference is as you get to higher lvl dungeons you play with more veteran players that have no patients for dying, unfortunately that's not a realistic outlook to have, this means that you will be subject to many a flame out for things that are entirely out of your control, this is sadly just part of the way people behave when afforded the anonymity of Internet gaming. Don't ever question your WHM skill, take solace in the fact people will always need healers, and if your using duty finder you will likely never encounter that person again.