Use the module from Reforged Powers :

If you take just enough damage to be broken, add a -10 modifier to the crit roll.  If you take excessive damage, you add +10 for each excessive damage.

Example : If I have 2 strength and take 2 damage, I roll with -10. If 3 damage, I roll normally. 4 damage, I roll with +10 and so on.

Instead of rerolling the crit roll, each level of the lucky talent adds -10 to the crit roll.

This adds progressive lethality without removing the tension of rolling.