I'll phrase it better when I can.
Cleric casting is pretty essential for a monster that normally 'prefers to solve encounters with spells' and has cleric casting 14 on what is normally a 12HD monster. I figured making it 2/3rds casting might leave some room for features; and caster level = HD seems to be pretty standard for these things. I just wasn't sure how many features I could slide into those lost five levels, so I overshot.
Did I remember to put in the part about the continual flames only lasting a minute unless some material components are spent? Yeah, OK. They're not exactly overpowering spell-likes, so I'm not all that worried about them.