The issue not in BH, but in the game mechanics that allows nonscaled true damage and poisons as well.
Poison damage and true damage are scaled with damage modifiers. they MUST NOT. cleric robe+food+boots give +100% damage, it means that pure damage from BG E+poison do 300+510 damage alone. And your IP does not matter.
Then we have thetford cape that has very poorly scaled with IP damage and is affected by damage modifiers as well. So 4.3 cape adds another 250 damage not linked with your gear or CD difficulty. So we have 1000 damage from E+cape+poison and 400-800 damage from Q+W that is scaled with IP. So BH can do 1400 damage in 4.2 or 1800 damage in 8.1 (because there is a soft IP cap on slayer). 6 times more expensive set adds only 28% damage.
And no need to mention that 1400 damage is absolutely devastating on stalker mode where ppl have 2100-2200 HP
The worst thing about true damage is that it just doesnt scale with IP. That means 4.0 deals same true damage as 8.3. That just sucks. It means it´s good at low IP ( such as t6), and it means its trash at T8.
Just make it normal damage. Ez then. True damage is just trash and i don´t like it.
My YT channel - Solo greataxe killing everything https://www.youtube.com/user/DhaosNK/video=7