Roll OVER versus Roll Under

By deaddmwalking, in Deathwatch House Rules

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I posted this in the PbP forum for my GM to read, and per his request, he wanted to have it posted here where people more familiar with the Deathwatch game could share their thoughts.

While I'm new to Deathwatch, I'm familiar with roll under systems, and advocate them for 'roll high'. The post is below:

This is kind of a suggestion, and kind of a tirade.
One of the big breakthroughs of D&D 3.x was the 'always roll high'. In original D&D, there were some rolls you wanted to roll low since you often had to 'roll under you attribute' but other rolls that you wanted to roll high (like attack rolls).
Roll under seems like it should be easy, since you're just comparing two values (which one is higher) and that might be true until you have to consider degrees of success. If you needed a 66 and you rolled a 38, how many degrees of success did you get (without using your fingers)?
The thing is, roll under is completely unnecessary . Let me show you a better way.
Example 1 - Your skill is 40
You know to succeed you need to roll between 1 and 40 on your d100. Obviously, that is 40 numbers. Now, imagine that instead of saying 'roll under 40' you rolled the d100 and added your skill (1d100+40) with a fixed Target Number of 100. If you're good at math, you already know that you need to roll between a 60-100 in order to get 100 or better. That, my friends, is a range of 40 numbers (just like roll under). The real advantage is that degrees of success becomes SUPER EASY. If you rolled a 95 (+40) you have a 135. Since addition is easier than subtraction, nobody has a problem with that. And subtracting 100 is WAY easier than subtracting 38 from 66. Clearly, if you have a 138 you can drop the 100s digit (leaving 38) and that's how much you beat the target by - giving you 3 degrees of success.
Example 2 - You have a 70 in the relevant skill, but you have a -30 for circumstances.
You might thing you roll 1d100 +70 against a target of 130, but that gets right back to the original problem. In this case, you add them to your existing modifiers so we're right back at 1d100 + 40 [70 - 30 = 40]. Since we already did the math, we know that d100+40 against a TN of 100 is EXACTLY the same as 1d100 (roll 40 or below).
I can understand why you might be reluctant to make the change in the game considering you're pretty new to the system, but I promise you, the math is absolutely solid. If you did decide to make the change, I think you'd find people grasping things much more easily.
My big concern is that we've been rolling so AWESOME when we're supposed to roll low that things could get pretty scary if we switch. But I know that people will have an easier time with the system (it's scientifically proven).
Just a couple examples with failures because they are just a little trickier than successes (but still easier than the current system).
Failure Example 1:
You have +40 in your skill. Against a TN of 100, you need to roll a 60 or better for a success. You roll a 32.
Result - 72. You can start from 80 (since your degree of failure was not as low as 70) and you know you have 2 degrees of failure. If you had rolled a 22 your result would be a 62 and once again you'd start from the next highest tens to determine your number of degrees of failure... In that case 70 to 100 is 30 - so 3 degrees of failure.
I know making a change to a core mechanic can be a little nerve wracking - you'd think there MUST be a reason why they do that - but there isn't a good one. Most game designers aren't strong with math and the roll under mechanic has been around so long that it's just accepted without consideration of alternate methods that produce THE EXACT SAME RESULTS but with less figuring.
Please feel free to move this (or create a new thread) if you like. I could also cross-post on the FF forums under house rules, if you like.

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Doesn't sound that bad to me. Might discuss it with my players in our next session.

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I am very tempted to move to this system.

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I do not see the problem with rolling under and figure out the DoS, actually I find it quite easy, where as your system of rolling over and adding your stat to hundred, seems very confusing and unnecessary.

But that is just my oppinion, and if you for some reason want to switch, then by all means do it. I just can't grasp what you problem is...

Another option is to adopt the rules on the subject from Dark Heresy 2.ed.beta, where you calculate the DoS by taking the first digit of you roll and subtract it from the first digit of your stat, plus one success for rolling under.

Example: You roll a 38, you stat is 66. You get one DoS for rolling under plus; 6 (from 6 6) minus 3 (from 3 8). Wich gives a total of 4 DoS.

RAW in all the previous 40K games would in this example give 3 DoS, one for making a successfull rol, one for 38-48 and one for 48-58, but not the fourth because, there is not a full ten from 58 to 66.

Edited by SolP
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I do not see the problem with rolling under and figure out the DoS, actually I find it quite easy, where as your system of rolling over and adding your stat to hundred, seems very confusing and unnecessary.

You appear to misunderstand. You do not add anything to 100.

As written, you roll d100 and try to roll under your target number. The target number could be 30, or it could be 70 - it depends on your skill.

The proposal is every target number is 100. You add your skill to your roll.

If your skill is 30, the check is 1d100+30 against a TN of 100.

If your skill is 70, the check is 1d100+70 against a TN of 100.

Outside of degrees of success, it doesn't make much difference, but most people are better at addition than subtraction. Since it works out the same mathematically (they're equivalent functions) there are a lot of groups that will grok it more intuitively. It also has the advantage of making 'roll high' universal for best results. Some players (especially new ones) can be confused by trying to roll low for action resolution, but rolling high for action results (ie, damage).

Finally, if you need to compare degrees of success to an opponent, this makes it trivial.

If I have a 70 in the skill and my opponent has a 30, I roll a 52 and he rolls a 11, who wins?

Now look at 70+48=118 versus 30+89=119.

I think it's easier to tell who beat their TN by more in the second example - it's fewer operations which means less time thinking about the numbers and more time getting into character.