I cleared the Elder a couple days ago with the same strategy I used before.

Clear the area before summoning, use the best foods I had (carrot soup, minced meat, and deer stew), then just fire arrow him til he died. Use the indestructible stone monoliths around his summoning area to block his ranged attack, and kite him around his summoned roots. It seemed easier tbh, but that's probably because I had prior experience with the game.

Fight lasted maybe 5-10 minutes? Didn't keep track, but he died reasonably quickly. I might have lost 1/3 of my health bar at one point. Overall though, felt pretty good. I did delay it a day because the time I was prepped and ready, there was one of those vicious thunderstorms going on around the spawn. Easier to fight when it's not raining.

Have not fought Bonemass, but if the first two bosses are any indication, he'll be about the same difficulty as before. Just have to be prepared, max out your gear (for the available level of work station), and prepare the area beforehand if it looks bad. This helped enormously against Bonemass before, so I'll be doing the old leveling everything above the waterline again.