In your example, it add to 8% damage and is critical for the transition from P2 to P3 in HSTR. Once the health gets low enough, you'll want two people to register damage without carrying into P3 and the phase will clear. It sometimes takes a couple minutes for it to refresh, but the combined damage does count.
The reason this is critical in HSTR is that if a player carries into P3, the TMR for traya and sabers will be pre-loaded the next time they enter. if everyone is using chex mix, that player won't be able to maximize damage and may not even be able to get the right sequence to execute at all.
