I don't think that Sawyer's approach is necessarily bad, but he's not really communicating well how he envisions it to work. How much impact does correct preparation have? If party composition, spell choice and all that stuff is basically just a matter of aesthetics or preference, and the game is about "playing your build well" or whatever, that sounds kind of terrible, since it arguably makes it harder to produce interesting encounters that would encourage or force the player to switch strategies. Doing the things that your character or party are good at over and over again is banal; having to come up with new ways to overcome their limitations is interesting. This is why going out of your way to avoid roadblocking players is a double-edged sword; it's not a bad idea in absolute terms, but involves dangerous tradeoffs.
I don't see any contradiction between "playing your build well" and "switch strategies". A given build is capable of participating in various different strategies.
Well, that's actually true. But again, there's one of those small semantic thing here. I think your build, party composition and so forth should impact what good strategy
is for your party - that's what builds are for - but it seems to me that thinking in terms of "builds" and solutions that "support" those builds often produces this situation where people don't consider options that fall outside the expertise of those builds.
To illustrate this, let's take Dark Souls. It's a game in which character builds are by no means
trivial, and the game does reward specialization by making your character more effective at doing the things he's good at, but efficient play in the actual
game often calls for flexibility. A lot of people have trouble with the game because they're stuck with their build. "I'm playing two-weapons-fighting, fast DEX build, and now the Capra Demon and those dogs keep killing me because there's no rooms to maneuver! Shouldn't the game support my build? This game sucks!"
Right, but Dark Souls is built in such a way that it rewards thinking outside your build from time to time. Even for a DEX character, sometimes - not all the time, but sometimes - it's simply best to do things you didn't plan your build for, like use a heavy, blunt STR-scaling weapon, switch to the biggest shield you've got, put on the heaviest armour you have found, or get some spells, and so on. Figuring out the best way to do things, within the scope of your character's stats and the equipment available to you, is a huge part of the charm of the game, and it would never be there if the game worried about things like making Capra "balanced" for DEX builds. This is why there's merit in having situations in which a particular character build or type is strictly sub-par; it's by far the best way to make players consider alternative strategies beyond that characters' strong points.
Now, as I understand, PoE is already halfway there; after all, PoE has no arbitrary restrictions like, say, wizards being unable to wear plate mail. What worries me is that it seems like Sawyer looks at this largely in terms of freedom and internal consistency - you
can do this and the system supports it because arbitrary restrictions are bad, but only if you feel like it - the game's not forcing you or giving you any advantage if you do. Well, Dark Souls doesn't
force you either, but from time to time you have a really good reason to do things like that, because sometimes you're going to a fight where it's just plain good sense to put some nice heavy armour on. This is the kind of thing I really hope to see from PoE - that sometimes, one of the smartest things you could do with the party wizard is to slap some armour on him and have him stab people. Not in every fight, obviously, but from time to time, enough to keep the player considering options like that.