I sent my ship an extra several hours out into the ocean to kill a big fish that had a very high chance of giving me copper. All I got tho was a battered chest. Really makes you reconsider ever going out into the deep again. It's a complete waste of time, apparently.
Going for monsters further out is worth it if: 1- there isn't a closer monster with the same drop 2- you're already out there for something else (like exploration or a different monster), and its faster to kill that monster than skipping it, finishing your trip and sending a new voyage out to the closer monster. If the monster takes more than an hour to kill, it almost certainly is faster to skip it and fight the closer one in a separate journey 3- for some reason you need davy jones chests, and the slight chance of a davy jones chest instead of, or in addition to the drop is worth that extra time 4- you're going to work or bed and won't be able to check in on things for an extended period, and you want to queue up a longer journey for while you're away In general, if there's a closer monster with the same drop, it will be faster to skip the more difficult one further out and finish your trip without it, and instead take a short journey to the closer monster after your first voyage finishes.
I get squat from both near and far monsters. Three days of sailing and I netted one piece of copper. One piece, what the hell midoki. In the past I was getting at least some materials but the last couple weeks or so I've been getting very very very few materials.