Motlen Blast bug on hiting monsters

Hi, so I've played this skill with about 7 or so classes (a couple twice) because I fkn love it even though it needs a buff with a mace with projectile or something ANYWAYS - it appears quite often that the molten ball will travel right through a monster without explosing on impact. According to the tool tip;

"Gouges molten rock from the ground and flings it at the target. The Projectile explodes on collision, damaging enemies and scattering shrapnel in a cone behind it."

This means in theory if theres no pierce in play (there 100% is not) this should hit and explode, it honestly doesn't it goes right through a lot of monsters, quite often I can screen record if you guys need to see it. Happens more often than not on rares and bosses, it's really weird. I dont think it's working as intended.

Please advise or msg if you want a video, happy to do one.