I'll provide some exmaples where buffs and nerfs are best practice:

Example 1: Job X has Spell or ability Y that is never used in the game because either a bug or poor attributes of the spell/ability render it inferior to other comparable effects e.g. it's useless. Best solution: Buff the useless thing such that it isn't useless. In this case, the thing(s) that are below par are best upgraded to be meet the expected performance standard.
Example 2: Job X has spell or ability Y that is being used more than anything else in the game because it trivializes an encounter or has unintended effects due to a bug or issue. Solution: Fix the issue or nerf the effect such that

In-context hypothetical example. Suppose people find out that an alliance of black mages can kill anything in the game in one go with three meteors, no other job can do it. Do we 1) Buff every other job such that an alliance of them can instakill a boss? or do we 2) Adjust Meteor so it is in line with the intended parameters? Consider the repercussions of each. If every boss fight becomes trivial by stacking 18 of one job, the game would become boring very quickly and people would quit. If Meteor was nerfed, some black mages would be upset but everybody would be having more fun overall.

Conclusion: Buffing isn't always the best policy.

Ask yourself if there is anything about what is being changed on BST that fits in either of these categories (Because I honestly don't know as I'm not a BST)