Raging Spirits + Amanamu's Tithe bug?

The Support Gem states:

"Supports Persistent Minion Skills, granting a chance when Supported Minions die for you to gain an Abyssal Monster Modifier."

Raging Spirits has the "Persistent" tag but when the spirits die from Infernal Legion III Support or Minion Instability Support I never receive Abyssal Monster Modifiers. Is this intended? Maybe the "persistent" tag on Raging Spirits is not actually applying?

Unfortunately tags on Raging Spirit are misleading. The persistent tag from raging spirit gem relate to the gem being a spirit reservation aura and not the minion part of the gem. If you take a loot at every "aura" gems they all do share the persistent tag because their effect is one. The raging spirit minions their-selves are not persistent because they do have a limited living duration.

I too felt into this trap, I've been very sad this interaction doesn't work.

BUT !

The best use for amanamu's, like you and I intended here, is by using Druid's "Wolf Pack" gem as wolves are considered persistent minions. The gem gives you 6 wolves (5 base, +1 from 20% gem quality) for 60 spirit, more efficient than any skeleton gem. You can use supports to help your wolves die faster like "Feeding Frenzy I" (minion take more damage), "Minion Instability" (Dies at <35% max life) and "Loyalty" (wolves take a % of damage before you and have less max life)

Wolves also benefits from support raging spirits don't to help you out such as "Essence Harvest" so you recoup % maximum mana whenever a wolf dies and such.
On top of all this, Wolves are also considered companions so you can benefit from companion's related effects.

Hope this helps, the real downside here is that wolves needs 60 spirit instead of 30 and spirit is hard to maximize.

Also,

If you don't want any benefit from having your wolves alive but stacking your amananu's tithe as fast as possible, you'd naturally want to use "Infernal Legion III" so your wolves will die a few seconds giving you all 3 max buff from Tithe for 20 secondes. Your wolves will respawn after 6 secondes and die after a few more so you're permanently under the effects of abyssal modifiers.