In my opinion, the road to 70 buff is a hinderance more than a help unless you know from the start that you will be leveling multiple of the starting jobs simultanously. Otherwise you pretty soon way outlevel the content you have unlocked. (I'm currently playing through ARR after the 5.3 changes with a character with the road to 70 buff, whom I only intend to play as healer. Currently I'm 53 sch, 50 whm and MSQ is only at 45. And this is while I have avoided rest xp and don't even do the leveling dungeon daily every day).