I think I’ve talked about this problem before but I can’t find the topic I wrote.
The situation is slightly better than it seems, given that slow weapons also tend to have stronger runes than fast ones. However, this is a general trend, and the runes aren’t perfectly balanced.
At the moment, it’s actually a strong strategy to charge the focus with a fast weapon to be able to use a rune on a slow one.
But I’d also prefer the focus gain per second for all weapons to be the same (even if you lose the tactic mentioned above), even if that means rebalancing all runes (also because they should be rebalanced anyway).
However, in the topic that I can’t find, I explained motion value and how use to balance weapons correctly because it seems that the developers chose to make custom settings for each weapon instead of having the same settings for all the weapons and then multiplying them for the Motion value.
A simplistic explanation of how the motion value system works:
Let’s say the basic attack does 1 attack every second that consumes 10 stamina, gives 10 focus, and does 100 damage.
If we have an attack that is twice as slow, that attack will have a motion value multiplier of 200%, so doing 200 damage will cause 20 stamina and give 20 focus (obviously, in practice it’s a bit more complicated when you start to kick in, you also have to consider range, stagger, the duration of the animation, and not just the time between one attack and another, and also the concept of opportunity to hit with a slow weapon and a fast one is different, etc.).
These calculations can also be done by modifying things that are not the attack speed, such as if you take the same weapon and make it consume more stamina, this must be compensated in some way, perhaps with more range, more focus, or more damage, etc.
Essentially, to each factor should be assigned a value, and each weapon should have approximately the same total value. Practical testing should also be done to adjust the weapon to the actual use in situations in the game. However, at the moment, the developers only do practical tests and manually change every value without the value tables, or at least that’s my theory (given that some weapons are very unbalanced).