Pertaining to if DoN and OoW are good expansions, I'd give you a big yes on that one. Omens is one of my favorite expansions. It seems Sony puts a little more effort into expansions that bring a level increase. There is good stuff to do though like faction quests, chasing your runes, and some decent xp.
DoN has the crystal system which is a good way to gear a casual player up. Especially the augs. I have just about every focus effect aug from DoN and they make my character much better (mana pres, extended range, extended enhancement, etc.)
As far as DoDH, yes most of the bad reviews pertain to the MM's. DoD has some great content and great gear from the spell missions, although most of them have tough bosses and you'll need some seriously geared people to do them. On the other hand some of the missions are kitable or doable with average geared peeps, and spell missions can yield some good stuff, being better than plane of time gear.
When I picked up playing EQ after a year off, OoW and DoN were completey new to me and I had a blast playing in and exploring them. Sorry to ramble on forever, but that's my 2cp (and then some) on the newest expansions.