Problem is, is that eventually every "choice" you get will be Min/Maxed and only 1 build will be viable. And then you'll get kicked if you don't conform to the build. SE devs will see which builds are currently META and they will use those builds and party make-ups to test out new raids and content. If the content is being balanced around a certain META, then you can bet your bottom dollar that that META is going to stay META. Then, in the next patch, SE will say "Okay we're redoing the skill trees!" and the same thing will repeat.

see: League of Legends, World of Warcraft.

You can say "well SE can balance around a bunch of different builds and party make-ups" well, that just leads to sub-par content overall and trying to spread yourself too thin. The content would also probably be ridiculously easy once figured out and the builds and party make-ups were min/maxed.