.Sometimes you want to reward players who do the hardest stuff, and sometimes you want to apply diminishing returns to the players consistently doing the hardest stuff to make sure they don't race away from the rest of the playerbase. For me, the most important factor involved in when to do which is whether the content is repeatable. If it can only be done once, I'm more in favor of rewarding effort higher. If it can be done repeatedly, I'm generally in favor of diminishing returns with effort above a certain point. Incursions are repeatable, so I'd be more cautious there. Same thing with arena: arena is grindable and repeatable, so the rewards do have diminishing returns for effort above a certain point.