I liked Vashjir - I really did. However the reality is that while Vanilla might have had "collect 30 furbolg fingernails" it was replaced by phasing and dragging your friends down to quest only to find out that all 5 of you are in 5 different phases. Dear fucking god was that annoying. World PvP basically is non existent in a phased zone and if you are getting ganked getting help is very difficult.
The net result of Cataclysm was that questing and levelling was made immeasurably more dynamic.
Let's face it, the amount of people who really care about world PvP is rather small. And not that many people would be negatively effected by the phasing either.
Vanilla had content that was explorable and diverse. Diremaul is a very good example. I can use raiding as well though. When I quit most of the raids consisted of zoning in and either being in one room or turning left once. Conclave, Baradin Hold, the one with Sinestra, the one with 3D, Malygos, ToC, etc. It was not very exciting. Recycling Naxx? Not cool. I enjoyed a few new mechanics and as a Rogue Valiona was very fun in the shadow realm and healing Valithria was cool but for the most part it was not that exciting when you compare to a zone like Karazhan. I might not have been a fan of the entirely red instance that was Molten Core but at least it wasn't a one room instance with nothing to explore.
Well, you're talking about raids and instances when I was talking about questing zones.
And your idea of explorable and diverse seems to be different to mine - the world in vanilla was very static, whereas the world in Cata changed. I remember gathering all the quest parts to mend the bridge in Lakeshire and wondered when it was ever going to get fixed.