At least they have the courage to try out new things (which is a very rare trait in the gaming business these days). Of course things go wrong if boundaries are being tested.
Sometimes an idea sounds great on paper, so they try it. It only turns out later that it doesn't work as intended. So of course they will revision or entirely abandon it (which is better than doing nothing at all).
Yes, they did some bad calls in the past, but ArenaNet is trying to look forward, and willing to take a risk. For that alone they deserve respect.
Calling them terrible system designers just doesn't do them justice.