I didn't play Runeblade for very long, but I really wasn't that impressed.
They have several skills that are essentially worthless, and their other skills are all copies of skills from other classes. You can make it work, and it is pretty good at 1v1ing casters, but that's about it.
Iceblade does not do anywhere near the damage the tooltip states, and I'm not entirely sure it's penetrating armor as it should be.
Runeword feels as though it should be useful, but I think the warm-up makes using it unreliable.
BladeDance is just a renamed cleave with an insanely high stamina cost. Cleave is already underused on most warrior specs, and for it to have such an absurd stamina cost for runeblade makes it unreliable in a real fight.
And since the nerf, Firewave is pretty garbage. (For both Runeblade and Pyro)
In general, I feel as though there's no "heart" to the runeblade. He feels like an abomination that was thrown together in 5 minutes. There's no true unique "feel" to the class, and I think that that is the real issue. You can tweak his damage numbers and rebalance stamina costs, but in the end, runeblade feels nothing like a true "RuneBlade". He feels like a crappy ninja with instant damage nukes.