I have had this game since it came out, gone through several playthroughs with the same character, and there is something that is bugging me a bit.

What determines the rate at which the weapon skills (One-hand, Two-hand, Archery) increase? Is it the weapon damage or the amount of strikes? The first 60-70 levels (70 on Archery) are no problem but past that it seems like it takes forever for the weapons to go up a level.

I ask because I frequently wind up with weapons that do an "insane" amount of damage but it doesn't seem to make the skills upgrade faster. I don't even use skill perks on the weapons categories now because of the amount of damage the weapons wind up doing without them. By "insane" damage, I mean damage upwards of 150pts.

On my last playthrough, I wound up with nearly every skill 90-100 except for the three weapon skills. (And my Illusion and Restoration skills which takes forever it seems, too. I can at least get them raised, though.) I seem to be getting stuck around level 75-78 on my character because of this. I'm trying to minimize my trainer usage (though you can't use them past level 90 for skill raising anyways).


On enchanting armor, what is the lowest percentage of Fortify Spells that would put the spell cost at 0 points?

I tend to prefer a "Stealth Mage" style when I am not trying to raise stats so this might be part of the problem.

Uesp claims it's weapon damage, not number of hit. however at higher levels it takes far more to level up than on low. Also the damage increase from perks and +damage enchants are not used however it look like tempered weapons level you faster, the bonus from sneak damage level sneak.
For zero casting cost you will need 4* 25% spell reduction.

It's base weapon damage * number of hits. Smithing and enchanting does not affect experience gain for each hit. Increased damage through perks and skill gain does not affect experience gain for each hit.

Damage improvements through smithing or enchanting slows down skill improvements because it kills your enemy quicker.

I sometimes carry unsmithed and unenchanted ebony or daedric sword to kill things to level up one-handed skills quicker, to use in easy battles and safe situations.

So it is better to use the untempered weapons to raise skills as oppose to smith swords that do 100+ damage?

Yes it's much much better to use untempered weapons for the purpose of experience gain.