Well as you guessed it, this will be SeekerFate's hell grind cbt locations. Note this won't be really that detailed, but it worked for me if your willing to spend an hour or two for a level at a somewhat decent rate in this exp hell with a group of people/friends.
lvl 1-9 This is mostly straightforward, just do the dungeons/quests you get and plow through tiamat (and/or get help) *Doing Training grounds,Kishinden(ehhh....),(daiku cave? according to friend),and cave of Karma on Hell is some decent exp to bolster your efforts through these levels*
lvl 10-16 Underground Cavern, specifically Byakkou's Cavern will probably be your best friend here, albeit boring as hell. Being able to do powerful aoe attacks really help with this grind. (This is also great place for getting some of the good lvl 25 weapons)
lvl 16-18 This can probably be done just by doing Izumo and some of the sidequests here. (If you need some supplements to exp here I'd reccomend maybe getting some more exp back at Byakkou's)
lvl 19+ Kyoto, if you've made it this far just pat on back no questions asked. (we know the feel)
I may come out with better locations later on and most likely I'm going to revise at least part of it when Open Beta starts but that remains to be seen for now.
Note:Byakkou is grind intensive but it provides some really decent rates (imo) for reasonable amount of time (with my group we could get roughly 1k exp per 6-7 mins on hard at lvl 14-16; we were doing it on hard due to ttk/exp ratio and the way we were grinding found it slightly more efficient but hell is the better choice pure expwise especially the faster you can clear it)
As for other notes um.... I'll list em later as they come.