In my game Channeling i'm working with a skill based system that was actually suggested on this board.
The system works by investing points into tiers, where higher tiers are more general, but more expensive to buy. So, a higher up tier may be as general as "melee combat" but is very expensive, while the same character could buy points in, say, "Daggers" for much cheaper. To figure out your skill, add up the applicable tiers, from top to bottom (assuming an applicable skill is available).

The hitch i'm having is trying to figure out a way to allow players to mix skills, to use more than one skill on a given tier for tasks which make use of both skills. Just adding in the other skill wouldn't work because that would give someone a much greater chance of success, simply by finding a way to mix in another skill.
I've had two thoughts, one would be to average the skills together, the other would be a similar thing, where for two skills, add half of each, for three, add 1/4, for four, add 1/8...
The problem with both of these is the math involved. Anyone wanting to do a complicated action would have to break out a calculator. The base system already involves a fair bit of math, but it's mostly simple addition.

Any other ideas, or refinements of mine, or else just saying that you don't think one of the above ideas is unrealistic to make someone do. Keep in mind that for the majority of skills, it will be simply tier addition, and only odd or complicated things will involve this. For example, if "backstab" was a skill, and "hamstring" was a skill, this system would come into play if someone tried to hamstring on a surprise attack...
... alright, bad example, but i hope the idea comes through.
Thank you in advance.

maybe better to assign wide focus skills with more points and not factions as you said.

So focusing on staves might a 1 point, two handed weapons 4 points, melee weapons 8.

Im not sure how your tier system works percisely, but If we assume the higher is better, then perhaps a simple bonus from the assisting skills' tier..

that is to say, if you have Knitting as a teir 1 skill and small blades as a tier 3 skill, then perhaps, Sally gets a plus +1 (her knitting tier)  on her attempt to stab Jon in the head with a knitting needle.

now assuming that Jon, as a chef at a Japanese Steakhouse & Sushi Bar has Cooking as a teir 5 skill and daggers as a Tier 1 skill,  gets a +5 bonus to deflect the knitting needle with his steak knife.

In that way it may not be granting them the full bonus of the assisting skill but still makes it worth the players time to consider supporting skill sets, and avoids requiring calculators..

-Skallagrim

Alright, i didn't describe the system very well... my apologies, it was 2am at the time... how about and example?
Currently, it is set up as a d100 (percentage) system, but that isn't set in stone, even if i keep the skill system.
Aussigamer had it pretty close actually, in a way... A skill line might be
tier 1: Melee at 10%
tier 2: Two Handed at 5%
tier 3: Bludgeoning at 15%
tier 4: Staff at 20%
and also has...
tier 4: Spear at 10%

In which case, this players skill with a spear would be 10 + 5 + 15 + 20 = 50%.
So they would have to roll less than a 50 succeed on the roll. Now, say he wants to use a staff as a spear. He could combine his spear and staff skill to account for needing some of both. the two ideas i mentioned previously would both give a total of 45% for this roll.

It's not a very good example either (in actual play, someone would probably just use their spear skill) but i hope it gets the idea across. Thats why addition doesn't work, because in this example, if the character tried to you his staff as a different weapon, he suddenly gets 10% higher chance of success!

Hope i explained it better, i actually did notice something else i need to fix about it, but thats for another thread (if i don't get it myself).

In which case, this players skill with a spear would be 10 + 5 + 15 + 20 = 50%.

Yes, there will probably be minimum skills at previous tiers, if just restrict min/maxing somewhat...
I think your right, the two ideas i had should work... i expected it to come into play more often, but after trying to think of a application for it... well, i know they exist, but they are rarer than i thought...

Continuing on, which of my two ideas do you think would work better? the averaging is simpler than the other one, but i may like the idea of your overall skill going down as you mix in more skills (averaging 2 skills gives you two halves (2/2), 3 skills gives 3/3, etc... the other method gives 2/2, then 3/4, then 4/8...) but that might get too much of a negative...
Then again, how much of a result can you expect when combining 4 or more skills?

Hi Brian,

I'm a little confused. What's wrong with just adding any relevant skills? Would there be far too many skills that might be relevant? Because, thinking from a realistic standpoint, I see no reason why they shouldn't just add whatever experience they have to their attempt to accomplish their goal.

Also, this is unrelated, and I know you were just giving an example, but is your example with the spears, above, an accurate example of what a character might be faced with in game? Are you saying that he really only has a 50% chance of success? That he will, statistically, fumble his attack as often as not?

the numbers themselves are not accurate. I'll figure those out after i have the system the numbers have to work with. and as for the adding, i want to keep people from doing things like... (keeping the same flawed example for continuity)
"I attack with my spear... but i use it as a staff, while standing on my head, and singing to myself [an obviously absurd feat]. Now lets see... add in my staff, spear, acrobatics, singing skill... well, i have 95% chance of success!"

I certainly see your fear. In the original draft of Divinity Horizons, we were doing a diceless system that was to depend on combining different traits much like what you're talking about. But the thing I realized was that, no matter how hard you try, there will always be a way to use rules in a ridiculous way if a player wants to. It's only the collective agreement of everyone at the table that really determines whether a game's rules are followed logically or not.

Does this help at all?

If you don't like the calculations, how about just determining a maximum? As in, you can have a max of one more skill to aid you, and from that one you can only get, say, 10 points. So for climbing while using your acrobatics (this would be one suitable example), you can have climbing as your main skill, and get up to 10 points from your acrobatics skill as a bonus. Any more acrobatics is nice, but not when climbing. Knowing how to do somersaults simply doesn't help, whereas the (slightly) added balance and grip techniques do. Hence only 10 points.

And your above example of using a spear as a staff while standing on one's head and singing would, at least in my view, confer hefty penalties, not give lots and lots of bonuses. Demand seperate checks for every action (balancing on head, reciting song), giving a cumulative penalty to all checks because the character is trying to do so much at the same time.

Qi

That's a pretty good idea, Qi. I may just have to gank it if we ever get around to finishing our diceless version.

Qi wrote:
And your above example of using a spear as a staff while standing on one's head and singing would, at least in my view, confer hefty penalties, not give lots and lots of bonuses. Demand seperate checks for every action (balancing on head, reciting song), giving a cumulative penalty to all checks because the character is trying to do so much at the same time.

The system is the same as the skills (well, they are essentially they same system,  magic is just specialized skills), and in that context mixing is much more common... for example, if you wanted to do a spell that was half fire, half ice damage. If i don't do the skill mixing, what would be a way to keep that system? maybe make a seperate skill that allows you to mix spells together? perhaps make it so if you want to mix the spells into one spell, make the rolls for both spells, only pay costs for the most expensive or for additions, and add/average the results as appropriate.