I can usually do fairly well against a lot of people on my melee ranger but there are a few people that I've run into that are pretty much invinsible. I play to 100% of my ability (dropping traps, using abilities at the right times, pet swapping, etc, etc) and these people have somehow figured out how to go supertanker mode and negate anything I attempt to do to bring them down.
The two I keep running into are a guardian and a necro (iknowright?).
The guardian the node camps and will just tank through anything you have to offer. If you get lucky with a bunch of crits he can just heal through it.
The necro will take some damage but just demolishes entire groups of people. I've seen her take down 3 people without going to a downed state with everyone focus firing on her.
I go up against these two...a lot...for some reason and I haven't figured out a way to get them down or even have them take a reasonable amount of damage. This doesn't feel like 'balance' to me. I know warriors can do a lot to increase their passive healing but they still don't give me half the problems these two individuals do.