I think I might already understand this, but wanted to ask the Meta-Mind anyhow. Take a Leonal, and add a couple levels of Ranger to him. Does this increase the "caster Level" of his Roar ability (which functions as Holy Word) or is that tied specifically to racial Hit Dice?
Spell-Like abilities as well, when you add class-levels to a creature, but not CASTER classes (though a ranger is a semi-caster, but I'm not sure if that's really relevant), is the caster level of Spell-like abilities bumped up? Again, in this example, the Leonal's Spell-like abilities are defined in their stat-block as CL14, and they (coincidentally) have 14 HD. Because the CL of those abilities is stated, it is a fixed value, even if that fixed value happens to be the same as its HD, so adding Class-level HD should not effect it... correct?