Originally Posted by
Rosmarinus
In a general sense it is true, but x3 actually reduces travel time: increased xp rates make it that the quests in the zones are actually enough to level, meaning you will hop around multiple zones less or not at all.
I would reckon x3 on vanilla should be same as x2 on wotlk. But even with x1 wotlk you have to hop between zones less since xp is usually enough to finish the zone with enough xp for a new zone. Now make that x2 which should put you in comfortable level or even 2 above next zone.