Cluster-Maker.

[Sarick]

Why not
6 Fire Crystal > Inferno
2 Inferno > Cluster? Just seems easier...

Because 6 fire crystal you'd need 15 total to make one cluster.

One fire crystal as catalyst 1 + 6 fire crystals as ingredients = 7 total crystals to make 1 HQ
One fire crystal as catalyst 1 + 6 fire crystals as ingredients = 14 total crystals to make the second HQ
One fire crystal as catalyst 1 + 2 HQ crystals to make 1 cluster = 15 total crystals.

If you want it easy this would be the best route at 1 lost.

One fire crystal as catalyst 1 + 5 fire crystals as ingredients = 6 total crystals to make first HQ crystal
One fire crystal as catalyst 1 + 5 fire crystals as ingredients = 12 total crystals to make the second HQ crystal
One fire crystal as catalyst 1 + 2 HQ crystals to make 1 cluster = 13 total crystals.

It's a loss of one crystal per stack but I think that would be acceptable.

The second one could just be HQ fire crystal as catalyst + HQ fire crystal = 1 cluster. No loss.