Over the past couple of days my friends and I have taken a crack at these and found them surprisingly doable. We're all in basic Qvic and MPG trial-level gear; for every attempt the main tank was my buddy [url="http://www.magelo.com/eq_view_profile.html?num=913767"]Lobot[/url], an SK with about 9850 HP and 2700AC.
Like the other posters, we found swamp was a joke - 7 characters among 4 people (Bard/Shm, SK/Clr, Monk/Shm, plus an Enc) was total overkill.
With mountain we added a BST and Mage to the above, was pretty easy too athough the initial pre-slow DPS was something of a surprise having just come from the swamp. The dragon slowed easily with Discord (then Turgurs took after one resist), and there wasn't really even any AE damage taken in the part group without PoVeeshan, and the group with Veeshan resisted 99% of everything.
The next night we decided to attempt the JP dragon based on the LOS-control techniques suggested here, although for my attempt I decided to use the tunnel to the friendly gnolls. We pull the dire to inside the tunnel to spawn the dragon (who didn't exactly fit), and this blocked the AE perfectly. Initially we had the clerics sitting outside on the hill, which turned out to be in AE rampage range, but the AE ramp was weaker than I had expected and it was just a matter of a few steps out of rampage range to heal safely.
This one we 3x2-boxed with Bard/Shm, SK/Clr, and Clr/Rng, and although the fight was simple a matter of endurance. Although it would have taken forever it would have been killable with just 4 of us (bard, tank, healer, slower), so while the extra Clr/Rng was a welcome addition I'd almost rate this dragon as the second easiest fight we did, thanks to using the zone geometry. Playing the shm, I had no problems getting the new L69 Discord slow in but Turgurs required both malos and HoS before it would land.
Plains was by far the hardest because there simply isn't anywhere in the zone you can avoid being in line-of-sight of the AE. There are a couple places where you'd think it would be blocked, but it isn't. Upon reflection we might have been able to position the dragon in the water to avoid the AE, but that would have been pretty annoying. As it was we just did a straight-up fight with 7 initially (Bard/Shm, SK/Clr, Clr/Rng, Bst).
This first attempt went horribly wrong several ways; initial aggro wasn't by the SK and the ranger and shaman got eaten as a result; even with malos and HoS in, the beastlord wasn't able to slow the dragon after the shm died. Even so, we would have won if it had not been for one use of a CH instead of a spam getting interrupted by the dragon's AE.
The biggest lesson from this was that the dragon's AE caused a lot of interrupts, so unless you have a crack healing team you probably shouldn't be relying on CH. Still, losing to one of these dragons is no drama: it's easy to get a cleric to safety since you can position the fight near a zonline, and when the dragon despawned after rezzing the dire respawned so we could simply try again immediately.
The second attempt (with the addition of a mage friend) went perfectly smoothly; I never got the dragon magic slowed even with using Malos plus HoS plus Balance of Discord, but once disease slow using Malicious Decay plus Grummus landed the fight was trivial. In fact, privided that you can get a slow (probably disease slow) to stick, I'd say this fight is perfectly one-groupable too.
If I was to try NK again, I'd simply spawn the dragon near a zoneline and have the SK+Shm work in tandem to get the dragon slowed with people just zoning and resetting the event until you get the disease slow in, at which point you can wear it down without too much trouble.
I'd certainly encourage people to try doing these events even if you only have access to smaller forces. They are hugely more doable than I expected - whether this holds true for DN is yet to be seen, but having completed all 4 of these dragons I'm going to feel a lot more comfortable asking friends to help with those events.