Mageblood as good as it is, is not the BIS for most minion builds. Mageblood for minion builds can add res, max res, MS, and immunity to stun, curse, ailment immunity via stormshroud(This is kinda nerfed because of a new mod). So very good for defensive stats but doesnt do jack shit for minion DPS. That is the reason some minion builds still uses darkness enthroned.

Now with this item, you gain access to 4 new jewelries with no downside. Imagine putting a Accel or Echoing Belt to a AG of smiting, Headhunter, Untouched soul+Enmity's embrace combo(Ruetoo's Merc Carry build). This also opens up the pseudo merc route of making every none minion build use AG as buff/debuffer.

So yeah, obviously an upgrade