I'd start by buffing melee, ranged and caster LBs.

They have not actually increased the relative strength of these actions since their implementation in ARR (HW for ranged), and every expansion they increase potencies for jobs normal actions. The result is our current situation, where it's actually often a DPS loss for a melee to execute their LB 1 or 2 and especially so for non melee DPS to single target theirs. Parses not going to players that use it is a player issue and not a balance one, so who cares about that. (Don't balance the game around arbitrary parsing rules)

Ranged should do as much as caster, for starters. It's strictly weaker for no reason even though there's basically only one fight where it's trajectory is superior when it's not already mandatory.

But, LBs were put into the game in a time when:
Direct Hit did not exist
The highest potency single attack was BLM's Flare at a real potency of around 476 (260 on paper)

Only healer lb3 has changed since (doesn't add to weakness/brink of death, and later the range increase), and only LB variance was reduced recently due to TOP.

Because they rarely design bosses with adds anymore (especially while the boss is also attackable), healer lb3 and tank lb are in a much stronger position relative to DPS than when we started.

As for healer lb1 and 2... Yeah they're about the same because 'nothing helpful most of the time' is still less than 'much weaker relatively'. Tank lb2 is still just as strong because it's always been proportional, and it even layers on top of all the party mitigation that exists today.