Nils and Tobold are talking about inefficiency and the fear of being sub-optimal. Both of them seem to feel that the drive to optimize is negative.
I disagree.
For a decision to be meaningful, there must be a right choice and a wrong choice. Taking the right choice makes it easier to be successful. Taking the wrong choice makes it harder.
Players optimize because there is a chance of failure, and no one wants to be the guy who is deliberately handicapping the rest of the team. The game is already hard enough. Why make it harder on the rest of your group?
Trying to stop optimization is futile. Removing the ability to inspect or dps meters just means that you don't get any feedback and can't see what's going wrong.
You can remove the decisions entirely. Remove talent points and different stats on armor. No more optimization. But that makes the game less interesting.
You can make the game easier. If there's no chance of failure, there's no point in optimizing.
You could make content less predictable. But this is no guarantee of optimizing. PvP still has optimal builds and, more egregiously, optimal group compositions. It just changes the focus on optimizing to be the most damage for the most situations.
And I don't think that PvE players like unpredictable content as you think they would. Faction Champs in ToC and Prince Malchezzar in Karazhan had unpredictable elements, and there was a lot of grumbling about those.
As well, unpredictable content can still be optimized. Think of Blackjack or Poker. It's unpredictable. Yet there are still strategies and optimizations for those games. Only now you have to take probability into account, which makes the optimizations far harder to execute.
You could rotate content such that the "optimal" build in Fight 1 becomes sub-optimal in Fight 2. Which is promptly followed by the playerbase replacing the players from Fight 1 with different players for Fight 2.
In reality, I think that most people who are against optimizing aren't really against optimizing per se. Rather, they are against other people optimizing for them. If they were the ones to come up with the "optimal" build and reveal it to the world, then they would be happy.
But it just doesn't work that way. My rule of thumb is to assume that there are people who are ten times better at this game than I am. And there are people who are ten times worse. The better people are going to come up with optimizations faster than I will. The worse people will not see what I see, and just perform at a much lower level, making grouping with them destined to failure.
For any meaningful decision in a game, someone will determine the "right" answer sooner or later. The good players in the game will figure it out pretty quickly. The bad players will never figure it out.
The best an MMO company can do is make sure that each "playstyle" is close enough to the optimal so that it is viable. But otherwise, it is impossible to have meaningful decisions in group play, and yet not have optimizations.