Endgame Summoner -- Garuda

[Sacerdos]

My rough calculations for the DPS loss of not casting Ruin:

You have 24 GCDs in a minute. In a minute, you'll cast 4 Bios, 4 Thunders, 3 Miasmas, 2 Bio 2s, and 2 Shadow Flares, for 15 GCDs total used on DoTs, leaving 9 GCDs for Ruin.

9 Ruins is 720 potency of damage.

4 Thunders and 3 Miasmas flat potency is 4 x 30 + 3 x 20 = 120 + 60 = 180 potency

Total DoT potency a tick is: 40 (Bio) + 35 (Bio2) + 35 (Miasma) + 40 (Thunder) + 25 (Shadow Flare) = 175.

There are 20 DoT ticks a minute, for 3500 DoT potency total over a minute.

3500 DoT potency + 720 Ruin potency + 180 Thunder/Miasma potency = 4400 potency total over a minute, of which ~16.3% is Ruin.

Thus not casting Ruin at all is a loss of ~16% of your DPS.

Edit: Forgot to include Miasma and Thunder's flat damage potency, 30 per thunder and 20 per miasma.