Thought this would be a good thought experiment.
Let's compare a +1 flaming burst longspear (1d8, x3) vs a +2 flaming longspear. We will assume improved critical, so a 19-20 crit range. Also for purposes of this, attack rolls don't matter. A roll of 19-20 will crit.
+1 flaming burst longspear.
Noncrit: Avg Damage of 9
Crit: Avg Damage of 31
Total Avg: 11.2
+2 flaming longspear
Noncrit: Avg Damage of 10
Crit: Avg Damage of 23
Total Avg: 11.3
So in this scenario, giving critical hits every advantage in the world, they don't even compare to the +1 they replace. Now, lets go to the big crit, the scythe, and see what happens. Again assuming improved critical:
+1 flaming burst scythe
Noncrit: Avg Damage of 9.5
Crit: 44
Total Avg: 12.95
+2 flaming scythe
Noncrit: 10.5
Crit: 31.5
Total Avg: 12.6
So in the absolute best care scenario, the burst property is just squeaking by. Feel free to check my numbers for errors, but if they are right I think it leaves little doubt that the burst properties are mechanically worthless.
Let's compare a +1 flaming burst longspear (1d8, x3) vs a +2 flaming longspear. We will assume improved critical, so a 19-20 crit range. Also for purposes of this, attack rolls don't matter. A roll of 19-20 will crit.
+1 flaming burst longspear.
Noncrit: Avg Damage of 9
Crit: Avg Damage of 31
Total Avg: 11.2
+2 flaming longspear
Noncrit: Avg Damage of 10
Crit: Avg Damage of 23
Total Avg: 11.3
So in this scenario, giving critical hits every advantage in the world, they don't even compare to the +1 they replace. Now, lets go to the big crit, the scythe, and see what happens. Again assuming improved critical:
+1 flaming burst scythe
Noncrit: Avg Damage of 9.5
Crit: 44
Total Avg: 12.95
+2 flaming scythe
Noncrit: 10.5
Crit: 31.5
Total Avg: 12.6
So in the absolute best care scenario, the burst property is just squeaking by. Feel free to check my numbers for errors, but if they are right I think it leaves little doubt that the burst properties are mechanically worthless.