Karan Boss trial 1 and Vamp boss trials 1 and 2 are excellent grinding spots, solo with a bracer.
Karan boss trial 1 is more party friendly, but the Vamp boss trials has a very limited map space, but with excellent potential for afking training.\
These places are better than tap 1 IMO. Very quick EXP, no running for a kill. Tap 1 is okay for single kill EXP, but if you have ANY AOE, it's strongly recommended that you grind at the boss trials.