Timeless Isle doesn't involve any grinding at all. You show up, kill a few mobs while walking around, and leave with full epics for your main and all your alts. I came back on a free week of play time, hopped on the isle with my one character for about two hours a day, and left with an almost full MS and OS of gears for my main, as well as one complete set for one alt, and several partial (5+ pieces) for 3 other alts.
That wasn't grinding, it was being handed free epics. No effort, no skill, just free epics for riding around on an island for two hours a day max.
Additionally, I was able to use said main to see every raid that had happened to that point via LFR. I even saw the first wing of SoO. There is no longevity in this game, even with not grinding. This game is officially dead unless they bring the challenge back, and not just as an option.