Yeah to summarize what people are saying, every build has its own strength.
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If you want a build that has no weakness, you won't find one. The strongest builds fail at times too, there's no "One build to rule them all" sort of thing in this game.
For instance, AR builds are extremely tanky and easy to understand and play in easy and normal, but might have issues in Hard mode due to lack of stealth and initiative in combat.
More trap oriented/Stealthy builds show up in Hard mode, although there are plenty of amazing "glass cannon" builds for HM as well.
I recommend Wildan's Sledgehammer Build for a good all around build for Easy-Hard.
http://underrail.com/forums/index.php?topic=1736.0