The Elder's power isn't great, but it can be useful. If you're doing a lot of building or smelting, and you plant your own tree farm, then using the Elder's power to clear cut 50 or 100 trees is helpful. That's really the only reason to use it.

The 4th power is only helpful when you need it (no spoilers). It's very powerful when you need it, and useless when you don't. Think of the Elder's power the same way. Eikthyr's power is more practical. There's almost never a time in the game where reducing stamina use from sprinting isn't at least a little beneficial. The 3rd power is the most powerful, but you shouldn't need it most of the time, and the 5th power has no real point yet.