Without meaning to put a dampener on the idea, I really can't stress enough and support the point Ragnar has already mentioned: you need a very good rex line. We're not just talking about breeding some 150 rexes together a couple of generations, but you will need to be stat farming for both melee and hp, breeding those stats into your lines, staying on for the hours required to 100% imprint them, hunt down some very good master crafted or asc rex saddle blue prints. It's A LOT of work, and ALOT of actual HOURS and even after all of this time with our bred lines, we're struggling after the new updates. To summarise: base stat melee of roughly 370 ish and hp of 9k ish isn't going to be enough for anything more than easy, even with fluffy support
I have some new stats to now breed into our lines and see how we go, but tbh I'm not holding high hopes considering the whipping I've been scarred with recently after the most recent updates. The bosses are simply harder now. And even if I was on the whitelisted server which is more casual and less competitive, I would personally only really feel ok with sharing the spoils of my hard work if I was working with another player who I felt was doing somewhat of the same work, or I was very close to and had been playing with them a while.
I don't know if this is just the pvp side of me talking, but I'd feel a bit used if I had spent hours taming/breeding the 50+ 135-150 rexes to get the stat combo I wanted, max levelling them all, hunting for the saddle blueprints, etc. Unless Munki is willing to spawn in element for you and give you all the engrams (which I feel may ruin the fun for some as it removes a goal from the game), someone will be doing A LOT of work that others will be getting a free ride off.
Maybe when I come over to the whitelist I may change my tune, but I don't think so lol I still feel I would only really feel comfortable sharing the same spoils with players who had put in a similar level of work to what I had done. If one of you is happy to put in all of that hard work breeding etc. and have others get the rewards for "free" (or heavily discounted by only supplying saddles or cave artifacts which is the easy side) then of course that would be you decision. I personally don't think I'd be comfortable with it knowing now the amount of work it is.