XP/kill would be easier, however, XP/zone is there because in DL there are massive minion waves. Yes farming is tiresome, yes people pop allies and log, I do it, level 35 with over 100k PvE kills. No one is noob because of the way they level, be it plat, farming, or allies. They make it XP/zone so you spend more time playing and more time buying. Nobody said you had to play it.
And in regards to Canis' point on PvP, yes there are a lot of people with the same build, however, there are people, including myself, who don't use the mainstream combo or skills, which makes it all the more challenging. PvP is a place to have fun and let go of the terrors of farming. So called pro or not. The game is for fun. =)