I'm also sure that competitive questing will in some cases be the result of limited rewards.

For example, if there's romance in the game, then it would be normal for the romance to be monogamous. The logical outcome is that two characters have the same romantic interest, then only one of them will be able to complete the romantic storyline. Hence, competition. I'm not sure to what extent this will be explicitly designed as competitive.

There are also other scenarios with limited rewards, which I believe were seen in the alpha footage. For example, one method of escaping the prison that you can only pursue alone. Hence, if you pursue this option, your companions would have to find an alternative.

These forms of "competitive questing" also seem to be present in the single-player version of the game. Except obviously with fewer arguments.