Det is typically a pretty low stat, but it's effect on DPS scales linearly. As I understand it, you always benefit more or less the same amount from adding more det, where other skills have diminishing returns at high values.

My view on the novus weapon is that if you're going to bother with it at all, you should make it complement the other options for end game to give you the most flexibility in your gear sets. But I don't really think there's a wrong way to do it if you're putting appropriate stats on it, at least until we know how future upgrades will work. Even without spending soldiery on and upgrading the burtgang/noct hoplon you can hit 519 without food and without any accuracy from your MH/OH, so it's all a quesiton of how much effort you want to put into juggling the rest of your gear.