Fire and Conflagration eh? May I ask what is the difference?
Conflagration by definition is a huge destructive fire, so it's size then? Well given how huge Primordus is I wouldn't expect anything else than it causing a conflagration.
I mean seriously ANET anything would be better if you have no idea left, like Primordus could be the Elder Dragon of Fire and Puppies.
EDIT: I have been doing some thinking about it and I turned my attention to Jormag, as Primordus is Jormag's weakness and vice versa.
So shouldn't both their dominions be opposites? Fire is opposite of Ice. In that case if Jormag's dominions are Ice and persuasion then Primordus' should be the opposite i.e. Fire and the other could be something like SUBMISSION Go ahead ANET you may use my simple yet fitting idea I won't be mad.