Glory Accumulation

I am not really understanding how to effectively build Glory to use the Spear of Solaris Huntress skill. Level 58 Act 2 Cruel.

I had thought trying to stun the enemy until it is heavy stunned is the path.

However I have invested in just every passive Stun build up I can slot that is within reach of my passive tree/build and very rarely do any enemies become Heavy Stunned/Glory built up for me to use this power it seems.

Granted I burn through trash mobs with two (3-4 power) companions, opening up with Rake/Stomp or LSpear (maxxed out passives for dmg/crits to High and Low HP targets) followed with Thunderous Leap and then double Whirling Slashes (+50% stun build up slotted in one of the WS).

Everything is slotted to play on the bleeds, lighting, crits and stuns.

Rarely even fighting strong Rares or Bosses does the SoS light up for use. Is the stun build up just broken/slow, I am killing shit to fast or just flat out missing how to properly build Stun to Heavy Stuns/Glory?

Is the SoS skill just useless given this setup and I should slot some other "finisher"?