One problem with the whole grind only approach is that at level 54 you have to get to the continent of Zandorya to stay with the mobs that are at level. That requires a quest chain that starts with Mysterious Torrog at Titan's Hill in Aotulia Volcano. Then around level 70 or 71, you need to get to the Continent of Balanzasar. In order to get the quest that takes you there, you must complete both main quest lines that start in Thunderhoof Hills and join into one at the end of Limo Desert. Then main quest lines are required to get to all the subsequent continents.
If you don't move through the continents, you will reach a point where you are 11 levels higher than the mobs you are battling. At that point, you can kill all the mobs you want, but you will never gain a single point of XP or TP.