Here's version 2.0
It occurred to me that as characters and monsters become more powerful, they might have additional "plusses" that may take them off the top of the table (results over 20).
I figure that should give them the possibility to generate additional damage.
My thought is for every full five points above 20, the attack should generate two more points of damage. That is reflected in the new chart above.
Of course a "natural 1" or any modified result lower than one is a miss and generates no damage.