I have noticed, that with bone curse half the conversion options are “use this if you want to die”. Keep in mind that in later levels you get hit by a ton of smaller attacks. If you get hit 20 times for 1 damage it usually isn’t an issue, but add in bone curse and that could actually kill you because each individual damage instance procs the bone curse damage.
The Aura option curses you as well, so you will die if you use it, this is for an aura that already has a heavy mana drain and a reduced area of effect.
The minion option curses your allies, which essentially means they will die almost instantly to trash mobs. All for a rather minor effect.
The only builds that would even concider these options are ones that are trying to reach such high numbers that they one shot bosses(as they are the only ones that can afford to be less tanky), but even then there are better bone curse options for damage.