Improving weapon properties with static DCs?

[Matticussama]

I'm fairly certain this goes better here than in the Homebrew section, but if people think I should move it there I can.

There are several weapons (Daggers of Venom, Javelin of Lightning, Thundering enhancement, Disruption enhancement, etc) that have set saving throws. That is fine at lower levels, but at higher levels that DC 14 save pretty much means it only matters on a roll of a 1.

What would be the best way to improve those saves so that they continue to function as the player levels up? I've considered having either be +1/2 character level or +Strength modifier (for melee) or +Dex mod (for ranged), but I'm not sure which would be better. I'm also willing to consider other options from the Playground, if people have an idea which they consider better. If I did implement either of those, should I adjust their base costs at all?

Basically, I want to make improvements that can help melee have nice things so that melee party members can keep pace with magic users in my game as we keep leveling up. I've also implemented several other boosts to melee, this would just be in addition to those other changes I've made in my game.

[Namfuak]

You might be better off basing it on BAB. If you want a small, constantly increasing bonus, you could do per point, or you could do a large increase per iterative if you want to reduce bookkeeping at level up. Either way, you could try playing a game where the DC increases at a rate of 1/2 or 3/4 per BAB (so if you did per iterative, it would increase by 3 or 4 every 6 BAB) and see if it works or needs to be higher/lower. Those numbers just seemed good in my head, if you wanted to be a bit more scientific about it, you could see about how often enemies at certain levels will succeed against it, and decide on a rate that you want them to succeed at, and then find a metric that puts you at about that success rate.