You've been able to do that always? Just about what is there. Leveling now is far from a grind comparing to older expansions.
Well, yes and no, except at lvl 5 you cannot interrupt a caster, never been able to (unless you count Tauren and Blood Elves (Before their Arcane Torrent was changed)). Commonly this demand is what is considered under the grind topic as well, if you need to eat/drink every 2-3 kills.
Unsure what the hell you are talking about, what is "Never lose"?
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Leveling has always been easy. The history just made it smoother and more compact with the level squish. The only time leveling was able to be considered hard was when Blizzard scaled the world by accident, and everyone was whining because a random wolf was eating their face.
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A very good point, three expansions later, the OP's idea of an introduction zone/content only for 10-60 would be out of date, we would be lvl 100 once more by then.