I disagree completely.

Many specs actually have a wide array of talent choices that have quite a large impact on their utility and how they function.

Fire is a pretty good example of this. On an encounter where there will be AoE damage, you know that you want to pick up Impact and Pyromaniac. If there won't be enough targets to proc Pyromaniac, or there won't be at least two targets to allow for Impact to be useful, then you can switch those points out into something such as Cauterize, or you can adjust a point over into Improved Blink if you need to kite something, or Invocation if you know you'll be interrupting.

Just as an example, Fire can be a pretty useful at kiting on Atramedes if you don't have any of the traditional kiting classes. Pick up Blazing Speed and Molten Shields with at least one spare point put into Improved Blink. You can use Mage Ward to proc Blazing Speed if the breath catches up to you -- allowing you to escape it -- and Improved Blink will allow for a much longer kiting time. You only lose Impact and Pyromaniac in doing this -- and one point in Arcane Concentration if you go 2/2 Improved Blink instead of 1/2 -- which doesn't contribute a DPS loss on this encounter because there aren't multiple targets.