I just leveled my Botanist (my first DoL class) from 0 -70 in a little less than 2 weeks, playing a few hours a night and only really focusing on it once my Main stuff (capping Tomes, Clearing Omega, etc.) was done. I did Leves and GC turn-ins up to 60 and then did Custom Deliveries, GC turn-ins, and collectibles (while grinding nodes in the area for MarketBoard fodder waiting for the collectible nodes to pop) up to 70. This not only proved a really efficient leveling path for me personally, but also allowed me to easily have enough scrips to keep my gear updated as I leveled, as gearing from the MarketBoard instead of scrips can break the bank.