I always though that crit = dmg increases when lava burst is taken out. Please excuse this very basic math and let me know if it's wrong.

Example:
You have 0% crit and hit for 1 dmg per spell. You do 100 casts, thats 100 dmg.

You gain 3% extra dmg from talent, that makes 103 dmg.

You instead gain 3% extra crit, making, on average, 3 of those 100 casts hit for 2. 97x1 + 3x2 = 103 dmg.