Our Mists® leveling packages are tailored to get you to level 90 as soon as possible. Staying at level 85 will make you easily ganked by the new level 90's; likewise, if you're level 90, you can have fun ganking the lower level 85's! :-) By getting to level 90, you will have the upper hand on the economy through the auction house. Players will want to buy the new greens and profession mats that come out and being level 90, it will make it easier for you to farm these items. Additionally, you will be able to start gaining level 90 PvP conquest points for the new season 12 arena gear since the level restriction for Rated Battlegrounds and Arena is level 90.
Drustvar is far and away the hardest Alliance zone, which is exactly why you want to do it first. If you have legendary items, they’ll still be usable, and if you don’t, this zone will still be easier early on than it will be later. Drustvar is also extremely fast and will let you jump out ahead of your competition in other zones, which means fewer players around to take your quest objectives.