So how I have been doing this is I plug all my artifacts into a spreadsheet and figure out how far from 70 I am. Then I figure out how far away I will be after I add the 5 or 6 base pieces to my suit ( normal leather ), then I calculate the enhancement resist bonuses into that and once again figure how far from 70 in each resist I am. I then take those numbers and divide by the amount of pieces I can mod in my suit, and end up with basically what I need in each category to have all 70s.
So for instance
I now know that I need to craft 5 studded leather pieces that Need exactly these resists when made out of normal Leather 2,4,11,10,9. After enhancing I will have the last 3 resist categories already at 70 with 0 imbues. So now I play UO lottery with sewing kits. I am up to 20k leather spent and I still don't have a single usable piece( I got one that had the 11 and 10 flipped). There has got to be a better way no ?
I think you're overcomplicating things. Think of the resists you need as totals... then shoot for that total.
Trying to get a tunic that is exactly all 5 stats just so is an exercise in leather wasting, as you've found.
Trying to get a tunic that is 2, 4, (9<cold<12), (8<poison<11), (7<energy<10) is actually pretty easy. The greater range you allow on each resist... the better.
Also... don't be so concerned with getting EXACTLY 70s across the board, the key is that you don't want to "waste" an imbue slot because you need to imbue a piece with 4 cold. Consider also the fact that for cold and poison resist in particular 69 and 70 are functionally equivalent.
VERY few things hit hard with cold damage. The hardest hitting cold damager I can think of is a Shadow Wyrm, which has a max melee damage of 35, 100 tactics, and ~1000 str. So 35*1.7*3.4 = 202. Well call it 200 for simplicity. A shadow wyrm does 75% physical, the rest cold - so that's 40 cold damage.
If you have all 70s in resists, and this beast hits you for it's max damage, you'll take 60 damage. I've killed hundreds (thousands?) of these farming hides, and I can tell you, this is dead accurate for their absolute max damage.
If you have 70 physical, but only 68 cold resist, you will take 160 *.3 + 40 * .32 = 48 +12.8 = 61 damage. At 67 you'd take 48 + 13.2 = 61. This is not a deal breaker for me - given that this is somewhat of an extreme case. Against the vast majority of things in the game you can almost totally disregard cold resist.
Magery has only Harm spell, which you probably wouldn't take 1 more damage from until you dropped 5 or more resist. Weaving and Mystic each have a spell - but not many monsters cast these spells. Against a necro caster you'll want to make sure your cold and poison are up there, because a Dark Father (for instance) can land ~30 damage past 70 resist with a wither, and probably similar with poison strike.
You definitely want to ensure Phy, Fire, and Energy are at 70+ - given that there are plenty of things that can drop 25 damage EB and 30 damage flame strikes on you or 60 damage fire breath attacks - past 70 resist, and most things hit with Physical damage.
In summation: don't be so rigid.