I gave the Watcher a shot solo as a bear. I can confirm you can easily get through to the final stage with just purple quest gear and at L58, however trying to take down those damn tentacles before they start healing was impossible for me. His roar (which so often caused half a wipe in the old days) did a whole 1 point of damage to me, or got resisted. His attacks were so weak that I even went AFK suddenly during the fight, only to come back maybe 10 minutes later and find I was still alive. It took intentional effort on my part to get him to kill me so I could leave the instance, and even then it was difficult to do. I then joined a group to 6-man it and it was a breeze, with no need for tactics, no wipes, not a single death, and barely a word said between us. Just over and done with in about 5, maybe 10 minutes, then on our separate ways.
Tangentially, someone mentioned they would only do Watcher with a small group so there's less competition for the barter coin, but I can't see why they even want it in the first place. As I said, I'm in all purple quest gear, and the teal raid/instance gear in Moria is terrible in comparison. You take a huge hit in physical mastery and crit rating just for a little more morale. I've found it's better to just hit the phys mast and crit caps with purple armour pieces from quests and a few jewellery pieces to help that along (and it's pretty easy to do so), then simply stack finesse wherever you can. Even for my tank gear, I just stuck on a load of morale/vit pieces and ended up with 25k morale unbuffed, able to soak up damage like a sponge. Fuck, I even started getting some tactical mastery for a healing build just to see and ended up at the outgoing healing cap on that, too.
If people ever needed evidence that the devs don't play the game and are completely out of touch with it, Moria's re-release is a clear example.