Prove it. Which designer might that be?
The ones that OK'ed the expertise feats. There is no other reason to O.K. these feats. If they're not meant to be stealth errata then they're blatantly overpowered. If 45% is supposed to be your base hit rate at Epic then a single feat giving you a 60% hit rate is overpowered. Its that simple.
I posted the monsters. I posted the fact that 16 stat starting PCs have a 45% chance against same level monsters without synergies. I posted several different ways PCs can gain synergy and improve their odds.
Same level monsters at a single level are not a representative sample of the base. The average hit chance changes from what is is in heroic to paragon to epic tier. This was the math he was explaining.
As well: Synergies typically require you to hit first, or are a limited resource. When you run out you run into a lot of problems. Enemies at higher levels have higher amounts of hit points and can absorb more punishment than they can relatively at low levels. An enemy might die in 3-4 average hits at low levels but there is no way that will happen in Epic.
Yours is a "player entitlement" argument. If a PC has a 60% chance to hit at first level, they should have the same chance at 30th level.
No, its not. Its a "The game will behave better in this manner" issue.
Nonsense. A 30th PC has many magical items and powers and feats that he did not have at 1st level. The synergy of multiple 30th level PCs is much greater than multiple 1st level PCs. It's a slightly different game with extremely different tactics at level 30 because of the additional plethora of options.
It is, for about half of the encounter, then you're stuck drudging through hit points. There are some ways around this but it requires a lot of ability management from players both in the character creation phase and the daily power use phase. Basically you need everyone to build characters around damage enhancing stances and to use one stance per encounter to keep DPR up.
Ideally, these damage enhancing powers would not be so much better than the burst damage powers, but due to the longevity needed to succeed in epic and paragon play the other powers simply do not compare.
If the 30th level Orb Wizard gets lucky, he locks down the Solo monster for a significant portion of the rest of the encounter. The math states that he SHOULD hit less often because his control effects are so much more powerful.
No, it doesn't. Wizards trade damage for control with the majority of their powers being d6 and low die count. They suffer no penalty to hit compared to their arcane equivalents. (unless you coun't prime shot on the warlock).
edit2: Also, since wand wizards exist and can get significant bonuses to hit to change one miss to a hit per encounter, it could just as well be said that they are designed to hit more often than others(if you're apologizing for orb specifically then we can whip out second implement since the orb ability is not dependent on hitting with the orb)
The designers would be total morons to give the same 60% chance to hit at 30th level that they gave at 1st level. Just because one designer added a bad feat to PHB II does not mean that all of the designers are that stupid.
You're now making the same argument you railed against earlier. You make an argument to a point then claim that the designers must also know this fact. And because of that, you reach a conclusion about the design intent.
This is a fair argument, so long as the "fact" is indeed a fact. E.G. "Gravity pulls things towards the earth, the designers of cannonballs know this and so the claim that cannon balls were designed to fly is spurious" Is a valid argument. But "Car's can fly and so the designers of cars clearly intended you to drive them off cliffs" is not since cars can't fly.
In the end, it all comes down to how well you can prove your point against how well he can prove his.
Edit: In the same breath you're saying that "expertise is not a problem" and saying that "the designers must be idiots if they gave people the same to hit at level 1 as they did at level 30" ignoring the fact that expertise does just that at the cost of a single feat
Having played some higher level games(as both a DM and a player) i've found both that "well specialized groups do not need much coaxing to beat high level encounters", but i have also found that "it takes a long time to beat encounters and a majority of that time is time where the encounter has already been 'won', but you're just grinding through enemy hit points."
Granted, the real test will be how it plays out when my current group(level 8, just finished Den of the Destroyer on the SoW path) gets up to paragon and Epic tiers, but i don't think it will play much differently.