Fantastic first post, fantastic thread. Kudos to everyone involved.
I posted it earlier, but I also believe that post-Guilds Dominion changed quite profoundly. This has nothing to do with the quality of the expansion (Adventure is one of my favourite expansion), but with the raw numbers. In pre-Adventures times (and pre-2nd edition) quite often you could see these games with 2-3 overly dominant cards and many ignorable ones. These were perfectly playable just by following the Quist ranking. You felt smart if you picked an unknown combo, but more often than not, someone else had already posted it on the Wiki or on fds. It was a good time for being a beginner, because a few simple rules always remained true (Trash down, Ignore Scout, forget Chancellor, go with Witch, Sea Hag or Rebuild, if nothing works better: Big Money). You could not compete with top players, but you could feel like a beginning expert.
Adventures's cards, events and the 2nd edition shattered these truths: Suddenly you would have 5 to 7 viable roads in any match and tweaking these to the ebbs and flows of the game became even more crucial. It is like Titandrake said: The games revolved less about knowledge of the 'behaviour' of individual cards, but about understanding about the general rules that govern certain card types. It became more interesting, but also more demanding. It is interesting to look at the flow of the expansions:
1) When you played with Base (1st), Intrigue (1st), Seaside and Prosperity you would see certain cards return all the time. Knowledge and application of their combos was essential. This could feel quite repetitive after a while. (Remember the Goko campaigns? ;-) )
2) When you added Hinterlands, Dark Ages, Cornucopia, Alchemy and Guilds, you would see certain strategies return all the time, still with many matches dominated by certain cards. Combos increased in number, but they were still essential to know for good players. This already felt varied and interesting, though after the 100th Rebuild / Witch / Mountebank game you started looking for change.
3) When you added Adventures and 2nd edition, you would see certain strategies return from time to time, but games started to become far more balanced. Combos hardly matter anymore, as now they are both more and less of them in any game: Far more small combos in any given match, but much less chance for an unstoppable combo to appear in you total amount of plays. You started to begin missing certain cards that you had not seen for quite some days in full random. And basically every game now became a surprise that needed to be studied very closely.
4) Empires just by itself upped the bar further: With Landmarks and all the new events, it became absurd to speak about cards without context. Even Silver now costs 2! It was not possible anymore to 'learn' a card in full random, because it could take weeks until any given card had a chance to appear again in a setup where it mattered. There are classical combos now that are even counter-productive, depending on the Landmark. I also believe that this is the main reason why people do not post more specific card articles anymore: Why bother with any specific strategy if the likelyhood of these specific circumstances to appear is so low?
Do not get me wrong: I do not see this development as a decline from a 'Golden Age' at any given time. The opposite is the case: I can play Dominion for hours and hours and every game is like a new world - to me this is the perfect game. Every new expansion brings this promise closer to fulfillment. Eventually I will get all the mssing expansion and I will spent my life, discovering all the subtle nuances. If you ask which game to bring to a lonely island, I cannot understand anyone saying anything but Dominion in its current state. It is literally millions of games, all in this enjoyable, clean and easy ruleset.
I do not believe that Nocturne CAN reduce the complexity. It contains at least 30 new cards that will alter each individual game further, separating them from each other, more than they have ever been. By then it might take you MONTHS to see your favorite card again, at least in a relevant context. You could swap any of the expansion in the development mentioned above and you would still have the sam effects in place.
I agree with crj: We are shifting away from this game of knowledge, where the perfect realization of the known priciples determined the better player. Dominion turns into a game, where looking 'behind the Matrix' is key for victory - the most abstract and flexible player wins. On an emotional level I find this a bit sad: It is tough to say goodbye to the wellknown heroes of ye olde time, that you hardly see anymore around: Farewell Chapel, Witch, Library. You had your great heroic deeds in the spotlight, now step back in the row and do your share of work, like all the other cards.
But you know: Just play Nocturne with Base only and you are back in the golden days, where BIG CARDS with BIG COMBOS mattered. (Historical analogy not intended, but now hard to ignore ;-) )