I'm struggling to see the Shiva set as anything but a healer's set, to be honest... do we have a source for all of this? I know it's "from the Japanese", but where is the Japanese from?

It'd make far more sense for casters to be Ramuh and healers to be Shiva, looking at it:

- Shiva's colours are light blues and whites, the latter in particular being most closely associated with healers - casters (particularly BLMs) are darker, deeper colours; purples, reds, blacks etc., like those of Ramuh.
- Lightning is a far more offensive, destructive magic than ice, better suited to casters.
- Shiva's gentle, graceful image matches well with white magic.
- The staff the model is holding is pronged and pointed, more like that of a healer - BLM's staffs in this game tend to either feature orbs or a more slimlined design. That looks like a WHM's cane to me.
- The model's pose is more typical of a healer; casters tend to be shown with a more offensive stance, weapon drawn and so on.

More than anything else, I find it very odd that a non-healer would be in white.