this has been reported over 2 years ago and still was never addressed
I think it is a bit of a tricky one to work with battlespirit.
Essentially, the tri-focus damage is determined based on the actual target of the heavy attack.
So a heavy attack against a player is already taking battlespirit into account.
What the problem is, is when a heavy attack is used against an NPC. Since battlespirit does not apply to them.
So, you can't just add battle spirit directly to Tri-Focus damage without essentially double dipping battlespirit on Tri-focus with heavy attacks against players.
Now, an "easy" solution, would be to blanket apply battlespirit against ALL enemies in a pvp zone, player or NPC, and then just halve the health of all NPCs in the pvp zones to keep the damage against NPCs relatively the same, but still reduce overall damage output.