but are they redesigning every detail of the ARM for higher performance like Qualcomm does w/ Snapdragon?
yes. Apple has purchased several companies that specialize in ASIC design and the latest A6 CPU is the fruit of their labor. It is very different from other ARM processors on the market so this should not be much of a surprise.
an iPhone is basically just a systems integration job, with the sophisticated core tech bought from elsewhere
To a certain point, yes. But using that same logic, all other cell phone manufacturers are even worse. And there is nothing wrong with contracting out design when a company requires a unique part. There are times you want to do it in-house and times when contracting out is the preferred solution. Apple performs more in-house design then any other cell phone manufacturer. Only Samsung comes close - but their displays are developed a separate division and sold to everyone so it really doesn't count.
My point is that you are greatly under-appreciating the difficulty and importance of integrating / specifying the various different system components. Combining the different hardware and software to produce an efficient final product is typically the hardest part - assuming it's done right. And this is precisely why the market for premium cell phones exists. If it was easy, everyone would do it.
By contrast Intel is still one of the leading CPU design companies in the world, and almost always has the most bleeding edge fabs. What's that worth?
Based on sales - less then iPhones. Don't forget the Intel is not the only designer and manufacturer of CPUs. IBM has their Power7 series which outperform Intel - if you're willing to pay for it. Numerous low cost, highly efficient, low power CPUs exist from other companies. So while Intel is impressive, their value is still limited by the market in which they operate - just like every other company. It's why they're trying so hard to break into the mobile market.