The best place i found for this was the Tremel Tree this can be farmed around lvl 15ish maybe 13-14. (XP stops at lvl 19)
In this dungeon at the very start 4 groups of 4 cross paths. If you pull them together in a group of 8 they are very easy to kill and award 3k xp. once both groups are dead. walk out and back into the dungeon and save / repeat.
you can even lvl bonds here.
Bond 1-3 are 1 fight each, Bond 4-5 are 2-3 fights each. (7 fights total for 5 star bond)
Very fast and easy with AOE damage.