Not really, because Ferumbras (and other creatures/bosses) aren't balanced like Characters in terms of the Health, Experience and Damage.
Ferumbras has 90,000 HP, a Sorcerer would need to be approximately level 18,000 to have that much HP. As a Knight, he'd be comparable to level 6,000, which is still extremely high for today's standards.
Ferumbras damage is really low though, and by himself I don't think he can do any better than a mage around level 350. If you consider the Demons he can summon, it would be higher, but still nothing slightly close to the levels above.
As for the Ascending Ferumbras (or the Mortal Shell), it only gets worse, it has a huge HP pool but isn't extremely strong in terms of damage anyway.