No. For one thing, they died easier, so while round one was tough, round 3 was easier. They also managed to miss with their dailies fairly regularly. For instance, the NPC cleric (who was supposed to help give the others staying power) died in 1 1/2 rounds, having only taken one or two actions.
It was an enemy party of adventurers, and their gear consisted of what was expected in the adventure's reasure parcels, plus some of what they had managed to steal from the PCs earlier.
That's odd, I don't recall you at our table that night.
The players work well together, and know their own characters better than I know every in-and-out of the NPCs. If this is a concern, it will be a concern in any combat where there is a large group of enemies operating with a single hive mind.
I had tactics decided beforehand (as advised by the DMG), and modified those on the fly, just like I do with every fight.
Also, the stats are not equivalent, because the PCs have much better gear, and gear is a large chunk of your effectiveness in 4e. The NPCs are using items from the PCs' wish list, so unless you've carbon copied a PC, that item is less than optimal for the NPC.
That's a good start for a theory. Have you run any experiments? Without actual data, I'm afraid I'm going to have to continue to believe my own experiences over your beliefs.
Not according to the books or my experiences. Again, have you tried this, or do you just have it in your head that it won't work?
The NPC design steps in the DMG say they're there to save you work, not because using PC stats is unbalanced. When there is a tool that can create NPCs with a few clicks, the reason for the DMG guidelines goes away. They're still useful, and mandatory if you want a full blown NPC from most of the races in the DMG. In fact, I prefer them to a one-click randomizer because I'm more likely to get powers that I want to play with, and combinations between NPCs that will be challenging. Plus they're easier to manage because you're not tracking very many things that don't fit in a power line (like feats, paragon path abilties, etc.).
But that doesn't make the other methods of NPC generation wrong, just different. I'll definitely create full blown NPCs again in the future, because I like the added feats, paragon, and epic abilities that DMG NPCs don't get.