[Any d20] 4d6-3 Gaussian for combat

[playswithfire]

For whatever reason, I spent part of this morning thinking of an alternative to the d20 roll for, among other things, attack rolls. Obviously, a d20 allows a horrible roll, a perfect roll and an average roll to be equally likely, which breaks from reality somewhat. I'm aware of the 3d6 option, but this restricts one to only 16 possible values and requires, if I remember right, a fair amount of finagling to rework the standard weapon threat ranges.

So, I submit a slight modification to the 3d6 roll: 4d6-3. I admit the -3 is weird, but it brings the numbers back to a more standard 1-21 range rather than 4-24.

Critical threat ranges are simple to recalculate; set the upper bound to 21 and reduce the lower bound by 2. The Improved Critical feat decreases the lower bound by one rather than doubling the range.
{table=head]d20 Range|4d6-3 Range|Imp 4d6-3
20|18-21|17-21
19-20|17-21|16-21
18-20|16-21|15-21
[/table]
I've given less thought to automatic hits, misses and fumbles, but something along the lines of:
Automatically hit and automatically confirm critical on 20+
Automatically hit on 19+
Automatically miss on 3 or less
Automatically miss and fumble on 2 or less.

I considered having the option to confirm a crit on a 21 and do triple damage instead of the standard double, since this only happens once every 1296 rolls, but it seemed unnecessarily complicated.

This whole thing may be unnecessarily complicated, but I'd appreciate any thoughts you'd all care to share.

[DaTedinator]

I like the concept, but like you said, it's pretty complicated. 3d6 is just simpler. Plus, I'm not sure about how I feel about automaticly confirmed crits and fumbles; granted, that's easy for a DM to just change, but yeah.

I want to like it, because it's definitely better than d20, but I really like simple things.

[ericgrau]

Buying dice numbered 0-5 and switching the system to 0-20 would help, or you could scribble over the 6 on existing dice. Or try to remember that 6 is really 0, but remembering often fails.

The problem with Gaussian systems is that people tend to roll average more often, so a creature with the slightest advantage over another creature will succeed on its rolls much more often, while one with a slight disadvantage over another will fail much more often. When figuring CR you must remember that weak creatures are even weaker, so it should take more to equal a regular creature. Likewise you want to give encounters closer to but still less than CR = party level + 4 (an even fight with around 50% chance of TPK), to avoid making fights way too easy. Because, again, monsters that were a little weaker than the party will now be much weaker. Then you need to adjust experience as if it were a lower CR, unless you're fine with giving out more experience. The worst part of all this is that CR is only a guideline, so you may need to further adjust encounters, and being off by even 1 CR may have a major effect.