After slogging along for the better part of two levels, my mage finally completed the quests in Vashj'ir. The zone offers underwater combat, a seahorse mount, possibly the best visuals in the game, and a main storyline that runs through something like 145 solo quests. Then you reach the end, and it turns out that the entire arc you've been soloing for hours is merely the lead-in for a group instanced dungeon.
In fairness, we have come a bit of a ways since 2007. The entire chain is not required to get the dungeon quests, which are found inside the zone itself. (Some of the early quests in the zone are going to be nigh indispensable for actually reaching the dungeon in the first place.) Meanwhile, the random dungeon finder makes it much easier to actually find a group for leveling instance content, though it did take me over 90 minutes to queue and complete the zone. Back in the Burning Crusade era, all the solo quests would have been required to even zone in, and then the story finale would have been a raid encounter that most players would not be able to complete.
That said, this compromise isn't really ideal for anyone. Group players don't get the backstory behind the dungeon unless they're willing to spend hours on quests that will not challenge anyone in decent gear. (You're also required to complete about a third of the quests for access to the Earthen Ring quartermaster, whose rep rewards include a tanking head enchant not available elsewhere in game.) Meanwhile, solo players will need to carve out a large chunk of uninterrupted time to actually see the payoff of their lengthy work through the zone.
In the end, players generally choose their preferred playstyle for a reason. Much as I understand Blizzard's desire to get group players to visit all the solo content they spent so much time on, and to get solo players to try the dungeon gear grind (the first two upgrades are free guaranteed quest rewards), this type of mechanic isn't going to change anyone's mind on how they want to play the game.