Greets!
I've played in all BWEs and stress tests that Guild Wars 2 has had since it opened it's prepurchase phase. While I've only skimmed through this particular thread and havn't looked at the article linked in the OP, I think I can describe my experience to add to flavor.
First of all; Apologies to the OP, I do not mean to insult you by not reading your article, but I would like to not spoil myself further as I wait for launch.
I was originally skeptical of Guild Wars 2, all the hype and that I wasn't too interested in guild wars 1 didn't make for a convincing sell for me, so I made sure I got my hands on as many previews and videos as I could several months ago. I had saw some of the gameplay and features, but they were all geared to look better than they actually were. I've seen such marketing ploys myself in the past, but I knew A-Net liked to not make cookie cutter MMOs that mimic WoW is everything. That, coupled with my minor but not entirely unexpected disappointment of SWTOR, I thought I may as well prepurchase when the chance came. If I don't go putting money down, what right have I to complain eh? Hah, tell that to my wallet.
So, as the BWEs would come and go, I delved into the engineer and guardian classes, setting myself up as a healer. Guardian was cool looking with a greatsword and I kept on making people crap themselves as they saw my little human flying through the air at them with the greatest of ease. As good as it was, I didn't feel that guardian was as dynamic for me as it could be, so I delved into Engineer.
To properly describe what it was like for me to play engineer, I'll have to describe the setup i made for him and the differing experiences I had in both PvE and PvP.
In PvE, I was running about in human lands, so I was helping the Seraph wage their war against the centaurs. That was quite a fight, especially after getting out of queensdale, as I would have to push into enemy camps with friendly NPC seraph and players, all of us banding together to kick some ass and take some ground. Took ground we did too, as when we cleared out a camp, the seraph set up defenses, patrols and held ground, only for the taken ground to be rushed by centaurs not even ten minutes later. Long enough to move onto your next target, but short enough for you to find yourself on the retreat if the action in another camp got too hairy.
Skill use in PvE is largely a similar affair to what you see in other MMOs, since you can pull and kite enemies around as you wish.
PvP is another matter though, I exclusively played WvW with my character, which was very interesting indeed. Skill use is definately different and this is where I'd describe my particular setup. My engineer for WvW was set up with a rifle for long range, flamethrower for short range and elixer gun for support. Mines were also a part of my setup and it was very fun blowing people off bridges with hidden explosives.
To share an experience, the last beta event placed me at a place called Etheron, which is a large castle on the right of the map with an inner keep and outer walls. Control of this castle is important, as it can give you an alley of attack right into enemy flanks either side of the lake on the right, which makes it a high priority. Whiteside Ridge, my server, had just managed to take this castle and the main force had already moved onto the left of the map, leaving me and a few others there.
I was preparing to move across the river, when I saw activity crossing the bridge south of Etheron. Curious, I checked it out and found thirty real players charging for my position. Taking a stand on the walls, I called out on /team to get some help, of which there were only six responders. The six people that showed up with me, didn't get there in time for the enemy to bust through our south gate and I moved up to meet our paltry defense at the inner keep. Thankfully, our defenders had already set up siege weapons on the walls and manning them to fire.
The next four hours were spent fighting a ever rising tidal wave of red, half an hour saw 40 people banging on our inner keep, then an hour later, fifty people. They just kept coming, but we just kept killing. This entire time I was playing support with my elixer gun, spraying my allies with condition removing goo and lobbing super healing elixers to those who really needed to get onto their feet. I cannot even count how many people I got back on their feet from the downed position as our last stand would continue.
Then, four hours into the battle, the sky would quite literally start to rain with fire and arrows. Indeed, it was like it was blotting out the sun and I would realise what was going on when I looked at my minimap. My position had six little blue dots near me, fair enough, then the enemies at our door... fair enough, then I saw it, a massive blue sploge of allies surrounding the enemy. The fire raining from the sky? Those were siege engines set up on the outer walls by the allied assault force that took the castle earlier, they heard about our bust up and eighty, yes ~eighty~ people were now pushing into the enemy's backside.
Never did I see so many people panic to get away from the angry mob of badasses.
TL;DR I really enjoyed it.