For the most part, this game targets solo players.
Therefore, you can play the way you want to maximize your enjoyment.
There are many ways to increase the games challenges, to include, choosing Traits that are not as good as the recommended ones.
But...who would do that?

One thing to try is, simply, playing with no Traits.
This would eliminate the synergizing of certain Traits & put more emphasis on one's play &, of course, each Hero one receives.
Considering the AI does not get these bonuses, that seems fair.
Another idea (for a challenge) is to just allow for the selection of 1 positive Trait or God forbid, 1 negative Trait for that matter.

Anyways, just some thoughts.