I do like the battle high system as a way to push players into engaging in PvP and rewarding those that do engage in PvP. But I think the system is outdated in the current format.

The battle high system was built for a time when jobs had little self-healing and often required dedicated healers to keeping them alive. But in the modern format, battle high is entirely too easy to get and maintain, so I do feel it should have drawbacks.

Since the biggest criticism of battle high is that it allows the team that's ahead to get even farther ahead, I'd say the damage up from it should come with negatives as well to balance it out.

My personal suggestion is to remove the healing received boost and add an 8% vuln up on every stack of battle high, so you'd have a whopping 40% damage taken increase at max battle high. Also, the healing received boost is overkill now that everyone can spam self-heals up to 4 times with no CD. These 2 things would make battle high a riskier thing to have, and it would also allow the teams that are behind to have a fighting chance since the team with stacked battle highs would do more damage but also die a lot faster.