Besides the increase in professional levels after ascension to godhood, the greatest enhancement comes from the attribute blessings granted by divinity and divine format.
Usually, weak divinity grants +1 to all attributes, lesser divinity grants +2, intermediate divinity grants +3, and mighty divinity grants +4.
The corresponding divine format blessings are the same; mighty divine power on the basis of divinity also grants +4 to all attributes.
This means that, when Shirek was a mortal, his constitution attribute was about 14 points, akin to a relatively strong mortal thief. After ascending to godhood, he immediately became supernaturally robust, and that's just in a normal state, not accounting for enhancements from other magic, divine power, or domains.
Once a mortal ascends to godhood, it's a complete qualitative change.
As for Duncan, he's just beginning, having taken the first step toward divinity; next is the law of divine format.
