If I recall correctly that's how it's always been with Diablo. I've remembered each D3 season there was a different build for each class that would work really well. So while the content was always kinda the same, the game forced you to try other builds if you wanted to beat the highest difficulty level consistently.

Looking at how uniques work at the moment they always seem to affect skills directly, groups of skills, weapon types or damage types. So if you want a strong build you have to get uniques that stack well and buff the same kind of tools you want to use.

Logically you want to buff one damage skill to the extreme but since there sometimes are no overlaps and uniques are sometimes skill specific, you run into the issue, that a different damage skill just doesn't do much damage anymore. This concludes in you essentially having to use actives and passives from your ability tree that also buff your one "super-skill" or boost survivability. Since you're not restricted when it comes to buffs, the most logical choice is then to just fill all remaining slots with buffs or skills that activate buffing effects. Even mobility gets pushed out in high end builds for more damage.

I don't like it, but as soon as you make an effect that only works in one context, you have effectively ruined build variety because theorycrafters will just min-max the hell out of it. There probably is no good solution that helps build variety and at the same time makes uniques feel interesting and exciting. Because when everything is viable, unique effects will mostly just be stat boosts and thus boring.