I just figure no party heal beyond Healing Breeze until Magic Fruit at its implementation helped BLU get its foot in the door for a front-line presence. Tying physical spell accuracy to main-hand also curbed the job away from staff swapping for everything. Even until Wild Carrot and other later goodies, Head Butt spam was arguably revolutionary as the game's quickest source of frequent stuns, and thus damage mitigation if used well. The job might not have brought the highest damage numbers, especially on HNMs without CASA Cannonball and proper support, but for most other things you could definitely find something to do for a BLU almost regardless of sub.