Your responses are completely and entirely reasonable, and exactly the problem. They DESIGNED this system (along with the sentient weapon system) to maximize selfishness and minimize helping others. I don't have a problem with how you are behaving. I have a problem that the system was designed to encourage such behavior.
A better system is to have sentient exp and reaper fragments completely separate from loot. Sentient exp gems can drop at the same rate, and the same value, as named items, and reaper fragments can drop at the same rate as reaper bonuses appear on named items. The problem is that the items currently have to be destroyed to get a benefit from the system. Let's remove that.
That wouldnt actually make anything different, or better. It would just make items themselves low-value, since they always drop without mods (or Mythic at best?). Few people would actually need the base item, and those that did would get it relatively quickly even without someone else passing it.
The long-term value would still be in the Reaper frags themselves, whether they're contained within the item, or exist as a standalone drop. People would still hoard all their Reaper frags just as they hoard Reaper items.
In fact that system might be a little
worse, because right now there's a small chance that you will get your item to drop with a Reaper mod already on it. In your suggestion, the
only way to get Reaper mods is to craft them on, so you're stuck until you get 50 frags, and again no one is going to pass you theirs.
Generally I think the better system is the one that doesnt create junk item bloat - and having the base items be separate from Reaper frags would mean base items are junk tier for most players. Keeping Sentience and Reaper value within the items themselves keeps them from becoming chest filler.