I’m playing a Spellblade and I just tried a respec with flame caller (flame reave returns to you).
With Rolling Thunder also specced (half flame reave base dmg converted to lightning damage), I noticed that the return wave visually only displayed lightning and no fire component. I’m unable to tell whether the damage is being applied correctly and its only a visual bug, or whether it includes damage.
I tried unspeccing Rolling Thunder and respeccing it again to see if it would fix, but unfortunately it did not and still only see lightning on return wave.
Without Rolling Thunder specced, the flames return as expected.