The "buff overland content" debate will never be resolved. So what about a compromise?
Many people see scaling overland baddies as a great on-ramp for new players. And they're right. You can safely travel the world without feeling like the prey of every living thing.
At the same time, this same mechanism is a steep off-ramp for long-term gamers who realise that endgame challenges in ESO really amount to: PvP, achievement chasing; housing editor.
Areas of self-contained levelled content could improve both camps' experiences, and potentially create new focus for the otherwise sandboxy PvE game we have right now.
Levelled content also provides fresh incentive for older players to roll a new character and start over. I came to ESO from Anarchy Online which is built around leveled dungeons. Playing through the three starter areas (Subway, Temple, Foreman's) gave you an immediate feel of every new character you created. You could tell when you had improved or hit upon a good build, because you breezed areas that previously you'd wiped in. You could solo bosses where previously you'd needed to hang around for a group. And best of all: you we're collecting all of the levelled loot which you'd missed last time you played through.
Overall, I like that ESO has chosen NOT to use levelled content. However, it is useful if used in the right context (contained environments like public dungeons). Introducing a handful of levelled dungeons might provide a new community focal point for the game, and would provide longtime players with a completely new set of challenges. Who was the first to solo the lvl10 dungeon final boss? Who managed it at lvl7...6...5....? Stuff like that.