I think it's clear that Zenimax wants to encourage more group play. I also think it's clear the only way they seem to know how to make this happen is making the monsters all but invincible to solo toons. Sure, with the right gear and skills many "invincible" monsters fall to solo players but lets get real, that gets old real quick. When they take away CC on many random encounters just getting thru some parts of the alliance quests are going to turn into a slog.
"Damn, I had to burn my ultimate on that Daedroth. And there's another one just 50' ahead. Time to turn around and kill half a dozen scamps to recharge the ultimate." Repeat ad nauseum.
So instead of fear being the motivating factor for grouping how about some alternatives? For example, what if each class gave a bonus to a party? Say grouping with a Nightblade gave your party 5% more gold. Grouping with a Templar gave you a chance to find two alchemy ingredients instead of one on plants. Grouping with a mage increased the chance of finding magical rings and necklaces. And grouping with a Dragonknight improved your chance of finding magical armor and weapons.
Sure, tuning these would take some time but I'd much rather there be carrots to encourage group play rather then the stick they seem to want to haul out. "Play in a group or die!" seems like a poor way to run a game. Especially when so much of the game is played solo. And, unlike the Ring of Mara, this idea would work for casual group play. That's another aspect to group play that Zenimax doesn't seem to grasp. Many players are casual, even someone like myself who has played hundreds of hours of this game but doesn't want to commit to a dedicated group.