Every single stat in Eden Eternal with the exception of movement speed, is multiplicative, so certificates like "Increase double hit chance 1%~2%" is just absolute garbage, as you can't even stack multiple such certificates across the board to reach a total of 7%/14%, the game simply doesn't calculate stats in the additive manner. (not that 7% total of double hit chance would be remarkably useful anyway... 14% might have been useful if you add item stats such as trophies or other things, but those also don't stack additive-ly, so meh)
And certificates that decrease malice by 5%/8% also seem very redundant when human healers have the "Snub" skill that decrease malice for players. Even if there are no human healers on raids, no one in their right mind would stack these certificates anyway, because again, game calculates them multiplicative-ly so its not additive. Speaking of which, if players end up using knowledge points on class talents that decrease malice then the numbers are also in diminishing returns when paired with the certificates...
Are there any plans to change less useful certificates into something more useful? Granted, it's probably not going to be things like "Increase crit by 50%" (compared to regular increase crit by 5%/10% certificates) but even ACC+5%/10% certificates are more useful in comparison and that's just sad.