I've made a few melee lists with blocks of daemonettes or the like that benefit from the skull cannon, but often find that the Soul Grinder is so much tougher--and has an AP3 gun, to boot--for only a marginally higher points cost, that can fill a bunch more battlefield roles. Still, striking at initiative when charging, say, plague marines in cover with a fragile-as-hell alpha strike unit like Daemonettes is pretty important...
I will be reassembling my kitbashed Flaming Chariot now, though, yeah. Give it some invuln buffs in game, perhaps, to counterbalance its fragility... who knows. Maybe it's not super-competitive--dunno yet, at this point--but it looks like great fun to use. And especially with the Heldrake nerfs of the 7e FAQs, I can see the AP3 torrent Chariot flamer filling a similar role--with an added serious anti-tank weapon option, to boot!
What sphinx of plascrete and adamantium bashed open their skulls and ate up their brains and imagination? Imperator! Imperator!