Tweaking Disintegrate

I love the flavor of disintegrate, I love the damage of disintegrate, I love the utility of disintegrate, I love the fact it reduces enemies to fine powder. I am even fine with having a spell attack and a fortitude save, well mostly.

I have one pet peeve with the spell; it is one of a very limited number of circumstances where you can hit and do no damage. That just feels bad. So I thought I would make a small adjustment.

I considered two possible changes:

-Switching from a Basic Fortitude save to a save with only save, failure, and crit failure conditions
-Moving the degree of success adjustment effect to the success condition of the spell attack. (If you read nothing else from this post, read this: DO NOT DO THIS. As I will discuss when I go over the numbers this is far to impactful a change, I have no idea why I thought this would be a small tweak.)

I wanted to test to see how often these changes would effect the results, and since I was waiting for something else to finish running I decided to simulate some dice rolls.

Now, I understand that this is strictly unnecessary. All you really need to do is calculate the intersection of the probability of a successful attack with the probability of a critical success on a saving throw. But generating random numbers is quick and easy, and I like seeing the probability play out in real numbers is satisfying.

So for this test I generated two samples of 1 million sets of 3 d20 rolls. Then to start I used the expected spell attack and DC of a lvl 11 caster and the moderate AC and Fortitude saves of a lvl 11 creature to establish the success conditions.

There are eight bins of results:

• A miss,
• -A hit followed by a critical save,
• -A hit followed by a regular save,
• -A hit followed by a failed save,
• -A hit followed by a critically failed save,
• -A crit followed by a critical save, -A crit followed by a regular save, and,
• -A crit followed by a failed or critically failed save

The last two success conditions are combined as they both result in a critical fail.

Using the stats described earlier I sorted all the rolls into their respective bins, seen below

Level 11 vs pl+0 with moderate AC & Fortitude

Bin	Sample 1	Sample 2
missed	450,118	449,300
hit, then crit save	49,820	49,694
hit, then save	250,475	250,254
hit, then fail	174,933	175,675
hit, then crit fail	25,158	25,080
crit, then crit save	4,914	5,014
crit, then save	24,647	25,036
crit, then fail	19,935	19,947

As above, but with sure strike

Bin	Sample 1	Sample 2
missed	202,540	202,871
hit, then crit save	69,658	69,322
hit, then save	350,943	350,188
hit, then fail	244,786	245,362
hit, then crit fail	35,234	34,974
crit, then crit save	9,715	9,783
crit, then save	48,113	48,843
crit, then fail	39,011	38,657

As original, but with heroism, off-guard, and aid

Bin	Sample 1	Sample 2
missed	99,668	100,235
hit, then crit save	50,134	49,556
hit, then save	250,167	249,867
hit, then fail	175,097	174,642
hit, then crit fail	25,277	24,927
crit, then crit save	39,714	39,869
crit, then save	200,111	200,481
crit, then fail	159,8323	160,423

As original, but with AC reduced by 2 and Fortitude increased by 2

Bin	Sample 1	Sample 2
missed	350,257	349,403
hit, then crit save	100,365	100,054
hit, then save	250,079	250,248
hit, then fail	124,676	125,130
hit, then crit fail	25,134	25,060
crit, then crit save	29,759	29,743
crit, then save	74,816	75,383
crit, then fail	44,914	44,979

Now this is where I figured enough of a pattern was visible. Roughly 5% of results are a hit followed by a crit save, which is the case I would like to address. Moreover the numbers themselves don't matter nearly as much as the relative difference between enemy AC and Fortitude. Fortitude goes up relative to AC and the percentage increases. AC goes up relative to fortitude the percentage drops. Makes sense. It also suggest that unless the difference becomes extreme, (which is unlikely as low AC is not often coupled with extreme Fortitude) then the number of effected cases is likely to stay within 5-15%.

Compared to the other change which would impact over 50% of cases and it's so fucking obvious that I shouldn't have needed to bother with this little exercise to see it. But sometimes you don't see the forest for the trees until your already out.

So, I'm now thinking of implement this little buff to disintegrate in my games, confident that it won't be too disruptive. But if it might only impact 5% of cases and disintegrate isn't cast all the time I'm wondering if the change will be noticed at all. Oh well. Maybe it's all for naught.