I think we have to allow room for more skills like Bristle to arrive. We have so much interplay between abilities already that allows for increases to potency on spells that I think it's safe to say more are on the way. Plus BLU was designed with the Blue Carnival in mind where enemies have specific vulnerabilities further increasing the potency of select skills. It is my hope that BLU will get a skill to scan enemy weakness in the future that can be used in all instances and open world too. If all enemies had specific weakness the lower potency of the skills would make a lot of sense. It's all speculation but Blue Mage could get really interesting in the future.