D'karr
Adventurer
I think the idea would speed up play -which is certainly a good thing. I'm curious what the impact is on some other aspects of the game.
I think that we can have the best of both worlds. The damage line for an effect can simply have the average/critical damage as well as the die roll expression. That way the DM can decide which one he prefers to use in a specific case.
For example:
Damage: 2d10+7 (18/27) Fire damage.
Alternately it can look like this.
Damage: 18/27 (2d10+7) Fire damage.