[Joseph Jostar]

Elemental Rune's element is not changed by the use of non-tome casting tools. Is this intentional? 

I've also noticed that non-standard-element tomes (such as Rexys, which uses blunt damage) ARE compatible with this. In such a case, what determines the elemental attack in the damage equation?

[Neus]

It's currently intended to only use a Tome weapon for damage type purposes, yes.