Andenthal's comment on Friday suggested a distinction between "outside research" and "additional research". I agree that there is a difference, but it is a blurry line.
Given enough time and perseverance, I would never need outside research for any game. Why not? Because given enough time, I can figure out any mechanic.
That's where I draw the line, on the vague continuum of "too much time."
I think we can agree that it is asking a bit much for every player to take out a few months to learn new mathematical techniques and gather data to understand a game. At that point, "additional research" has clearly crossed into "outside research".
Beside the time cost, there is that future use consideration. Is a +5% damage to elementals good? Yes? I'm sure it is useful, but how useful relative to the talent/perk/slot it is replacing? We can play play ahead and see how often we run into elementals and how challenging these are, thereby having the data we need to evaluate the usefulness of the +5% damage to elementals talent.
At first glance we might call that "additional research". It fits better into the "outside research" category. This is information which is unavailable on the first play, so right there, start the game, you need outside research in order to properly evaluate the talent, barring dramatic game actions such as NPCs using all their conversations to talk about how hard it is to kill elementals.
Developers could negate this issue by making talents easy to change, so if later on you encounter many elementals, then you can switch for 5% more damage against them. Or they could make it easy enough that whether or not you have 5% more damage against elementals, you will still beat the game with minimal profanity. These are both side-stepping the issue of whether the game is self-contained, by which I mean, if you play the game with some thought and consideration, you will, without opening Excel, know enough to make good decisions. Not necessarily the best possible decisions, but good decisions.
Now if you'll excuse me, I'm running 50,000 pirated copies of Skyrim on a botnet to determine the disposition change formula based on either number of units traded or value of items and I need to get this done before the FBI or Russian Mafia get suspicious.