So you think it was rigorously tested and reiterated over time? I've never heard anyone make that claim about 4E before.
Not particularly, though I imagine there was some of that (I mean, at the time I read reports from WotC people talking about doing that and they probably weren't lying). I think that those Warlock powers that I posted are counterexamples to the claim that
options were designed in such a way as to be easily comparable. This has to result in a trade off in breadth. For instance, how is communicating near-instantaneously with someone 100 miles away (Ambassador Imp) easily comparable to being able to fly but not atack for 5 minutes (Shadow Form) or teleporting up to 30 feet without requiring line of sigt (Warlock's Leap)? Even if a player is interested in combat potential, there are three escape options there: become intangible and fly away (Shadow Form), negate one lot of damage (Shielding Shades) or teleport out (Warlock's Leap). Are these easily comparable?
And where is the lack of breadth?
What if I want to trade off my combat capability to become really good at skills - I can't
There was a PC in my long-running 4e game built exactly along these lines: an invoker/wizard whose Epic Destiny is Sage of Ages. At 30th level, of 18 feats 6 directly buff skills and/or grant knowledge of languages; one grants a familiar which is not primarily a combat option but further boosts skills; one is a multi-class feat that gives a skill (as well as encounter power Thunderwave); one gives knowledge of the wizard spell Arcane Gate which is not really about combat ability; one grants at will teleport 2; and maybe other not-very-combat-y stuff that I'm missing on a quick skim of the sheet.
The character's main schtick is skills and rituals. His ritual book has 50 rituals; on a quick look through maybe there are a dozen or so rituals there that he hasn't cast at least once.
Across the five PCs he has the lowest AC, by far the lowest Fort defence (6 behind the next lowest, the ranger-cleric), the second-lowest Reflex (equal to the fighter/cleric, ahead of the paladin) and the second-highest Will (equal to the paladin, one ahead of the ranger-cleric, and behind the sorcerer/bard). His hit points are just over half the defenders' (139 compared to 222 and 224; and only 7 surges, whereas both the defenders have at least double that number - I think 14 for the paladin and 16 for the fighter/cleric).
This character has traded off combat capability to become really good at skills and related stuff. It's there on the sheet and it reveals istself in play.