Ok tested GLGS Dance at covenant rank +3 with the 45 Dex / 50 Faith with no rings nor crown on the Burg bridge hollows:
691 damage. Casting speed around 3 seconds.
Fire Tempest without rings nor crown, at 230 mag adj, same hollows:
807 damage. Casting speed around 2.30 seconds with 45 Dex.
At 16 Dex:
Fire Tempest: speed around 3 seconds
GLGS Dance: speed around 3 seconds, same speed as 45 Dex.
So Fire Tempest seems like the better option, also has more AoE. Meh, GLGS Dance looks badass.
691 damage. Casting speed around 3 seconds.
Fire Tempest without rings nor crown, at 230 mag adj, same hollows:
807 damage. Casting speed around 2.30 seconds with 45 Dex.
At 16 Dex:
Fire Tempest: speed around 3 seconds
GLGS Dance: speed around 3 seconds, same speed as 45 Dex.
So Fire Tempest seems like the better option, also has more AoE. Meh, GLGS Dance looks badass.