The gold standard for BLU leveling is to simply use the clionid and larva mobs in the tempest: aggro larva, let a clionid eat it, get showered in exp. You can do this pretty much from level 1 if you're a bit careful, and get to level 80 in less than an hour iirc. (do set your home to ondo cups tho, because you are going to die a few times)

However it is recommended to get flying sardine from apkallus in bloodshore before you outlevel them so much that any attack one shots them (a problem that you can avoid with other mobs because you can aggro them without killing them with flying sardine)