And the worst part is that the 3 globals combined for DoT's do not match in damage the global spent for a dire cast under astral fire. In order to start matching Fire with Astral stacks alone you need to have 4 DoT's on target, with the pet and casting ruin concurrently.

That isn't even figuring in the damage the BLM gets with Thunder on top of his 500ish fire casts under astral fire.

The whole point of DoT's is that their instant and they do more damage since they take longer to deliver over a period of time. But if a DoT bears marginal benefit over a direct damage spell, and it needs to be cast, with several of them needing to be layered to match the effect of a single spell, that's a problem.

And we're comparing against BLM, not BRD or DRG or even MNK who rank higher in DPS output.