(Posted updated, more in-depth version here
https://forums.totalwar.com/discussion/294311/rune-of-wrath-ruin-seems-to-have-infinite-cast-range-when-cast-over-walls-edited-w-replay-info )
Casting Rune of Wrath & Ruin way out of range:

It casts just fine:

Even works on the Warp Lightning Cannon way in the back:

(Link to the pictures on imgur in case hotlinking doesn't work for some reason:
https://imgur.com/a/lFlXC0n )
The bug works regardless of whether the rune is cast from Thorek or the normal Runesmith hero. I have not been able to test this on normal maps yet.