3-5% is never gonna happen, there are too many variables for the gap to be that small. 25-50% is not great, but it is achievable and certainly better than what we got now.
I would allow 25-50% if the other could also, instead of dealing 25-50% damage, survive an equivalent amount of damage, or have control that allows him to deal the same damage to receive the same amount or less damage.
This is called balance, when we are able to understand the difference and balance it with something else. That’s why I claim that Blizzard doesn’t understand anything about balance. They are still not clear which classes belong to which type. And how it is balanced. You just need to create and balance equivalents. And in this game it’s simple because there are only 4 character characteristics. Not 7 or 12 as in some games, but only 4.
You can’t just create a balance. It needs to be built. Sometimes by trial and error. But you must first at least want to achieve it.