Increase DMG or Damage me 
I testes it, if you combine both, it will kill you if you have any kind of hp on hit bigger than your hp pool. That means you can kill yourself ^^
So these two are in conflict 
Yeah becouse you have so little hp becouse of glasscannon. For example you have 1/1 hp after 100% glasscannon and you have 400 hp on hit. Masochism will hurt you for 400 hp becosue you are full hp and thus kill you. But i think you can use masochism and 100% glasscannon if you don’t have any kind of hp regeneration = 0 hp on hit 0 hp regeneration. It will not hurt you then probably becouse you don’t have sources to heal up but you will benefit from masochism.
So 1 HP is not increase dmg
Yes, i forgot you need to be 75% hp or lower. You can try to get like 95% glasscannon and have your hp at something like ~5000 and have hp on hit/hp regen.
My hero is wizard.
95%Glasscannon=260 HP 
I need 5000 HP Regen?
Test and get some regen but not too much becouse it can kill you 
I understand.I need HP more than HP regen Otherwise, it’s very easy to kill myself