Duties aren't like FATEs where you get a reward based on the tier obtained, and even then the weaker or less contributing player can just join a party who can do all the work for them yet still get the full reward in the end

It is frustrating when you go out of you way to perform well in a duty and you see one or two not making the effort or dying a lot. Though we shouldn't confuse inactivity/lack of interest with trying and still dying, most content is intended to be accessible and rewarding for the casual player regardless of how they perform. The majority of content can also be run several times to obtain any intended loot, a lot unsynced but all of them can be PF'd with the Loot Master having control so that's probably the best option to look at.