I'm curious about the part where you think my option 3 (moderate scaling with skill's speed) will "force" players into using faster and faster attack to maximize his procs. Yes, faster attacks will lead to more procs but reacher faster attack speed values will be less effective than for example, gearing to improve the unit's damage or even the proc's output. Since I'm proposing a scaling a procs compared to attack speed that is inferior to a 1:1 ratio, I'm hoping it will prevent that going crazy for attack speed is the only way to use procs efficienctly.
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I've taken care of the advantage of using a fast weapon (easier to react to rapid changes) in the general damage/speed ratio of weapons. Having procs be flat out better with fast weapon would have to be factored in my initial weapon balancing. This is completely feasable. It may however make slow weapon only good for damage and fast weapon bad of dealing damage since procs can be very powerful on very fast builds and thus the damage output of fast weapon would need to be really low. :/
Yup, that was the situation I was referring to (not that proc uses forces speed, per se, but that speed forces greater and great proc focus). Basically if the game is well balanced you probably won't see slow attackers using procs, or pure DPS fast attackers. That could be fine, but it's a loss of valid customizations. That said, it does make the general balance problem easier if you're willing to focus on a slice of valid builds and let non-standard builds have expected poorer performance. Note that this is basically the observation that even though option 1 exacerbates the issue, it's still an issue at some level with option 3.
This seems to refer to a full normalization of proc power (option 2). If I understand your reasoning, you are saying that this is a good option because it is balanced against the different battle set-up when slow attackers will be better than fast one depending on what kind of enemies / formation of enemies they encounter? This is a good call in theory and something that would likely help achieve a smoother balance of the proc system :) Sadly in my game, there is no such thing as fights are more like a Final Fantasy 7 battle where situational awareness, positioning & reflexes are not factored in battle.
It's kind of option 3 with a big caveat. A 40 turn attack might causes 40 ongoing damage. A 10 turn attack causes 20 ongoing damage. So after 40 turns, the faster attack has proc'd a lot more ongoing damage. But there's limited or no stacking, so actually if all 4 attacks were against the same target, it only has 20 ongoing damage. To get the full 80 point of possible ongoing damage the attacks had to be distributed among 4 enemies. The viability of that approach does depend on the larger combat system.
If you've got various skills with different effects, you might want to consider a reverse option 3 more seriously. It does break a certain expectation (maximize speed to get the most procs in), but it sort of feels like it fits the combat roles better: the slow attacker has a few important decisions about which powerful proc to activate (and then waits around for the attack to finish). The fast attacker is then responsible for using his greater flexibility to deal with the stronger effects his opponent is dishing out.