It's exciting to see a lot of good fight mechanics appear in the open world, but people are very slow on the uptake. I blame the UI, personally - that little row of icons up top? No good for the masses.
An example is the Canoneer fight. You can kill him in a few minutes, easy - but he's the Mai Trin fight, you have to lure him into the lasers to remove his reflect stacks. Once they're down, you burn him fast.
I just watched people fight him for 35 minutes. Every time he aggroed on someone, they'd just keep attacking and kill themselves off the reflect. Repeat as he aggros on a new person, until eventually I lured him into a beam, then his HP went down 25% instantly.
Great mechanic, but poor communication letdown from the UI. (Yes, I told people in /say what to do... but y'know).
Then there's the Knights, a nice see-saw between condition builds being best, and damage zerk being best - but people aren't "getting" it persay. Yes, it's the first day, but I've been playing GW2 long enough to know that it only gets a little bit better in a few days, then drops off again. Marionette was a good example - nobody could do it, then everyone, then nobody again.
GW2 does, in my opinion, need a complete and total overhaul of the traits system, and the way the UI communicates fight mechanics. Even so.. - man this patch is fun.