None of your arguments or points has any relevance to the fact power creep has done zero to combat difficulty - otherwise why on earth does this thread exist in the first place? PCs were wiping the absolute floor with monsters in paragon/epic from the start.
You are confusing certain powerful builds from wiping the floor in paragon/epic with everyone wiping the floor in paragon/epic.
That did not happen. I ran an Epic encounter with pretty average PCs early on and it was long and grindy and the PCs got popped pretty hard.
You keep harping on the super powerful builds and options possible with just the core rules, but that does not mean every single group used most or even a significant number of those powerful options.
The reason this thread exists is because monster damage was increased.
The reason monster damage was increased is because encounters at all tiers became so easy.
The reason encounters became so easy is because of all of the increased synergies of PCs (synergies that monsters did not significantly get). A small percentage of that comes from the PHB, but the majority of it comes from the other two dozen plus hard bound books, and the dozens of Dragon Magazines.
The PHB has 31 of 532 Paragon Paths.
The PHB has 4 of 101 Epic Destinies.
The PHB has 720 of 8977 Items.
The PHB has 707 of 7531 Powers.
The PHB has 161 of 3051 Feats.
The PHB has 8 of 60 Classes.
The PHB has 8 of 38 Races.
The errata has 23 pages for the PHB out of 123 pages overall (and some fraction of that is rules, skills, etc.).
The PHB is a super tiny drop in the overall bucket of everything with regard to items, feats, powers, races, classes, paragon paths, and epic destinies. The vast majority of game elements that determine PC power and versatility.
Sorry, but anyone who thinks most of this power and versatility comes from merely the PHB and not from the dozens and dozens of other sources is not being objective.
Yes, there was some significant PHB errata, but it doesn't mean that most groups wiped the floor at Paragon or Epic when the game first came out like they did immediately before the monster damage increase.
They did so then because of feats like Expertise. That one type of feat is a huge percentage of increased damage at Epic and it's a single feat.