If you give one class the advantage the other two have and more, you're gonna have to do that for them too or else there's no balance. Where will that lead? To classes being merely different character skins. That's not the way to go.
Creating environments and situations where a specific class's skill is the only way through would work. Or cross-class combos to make up for the dps loss and party buffs for having one of each in the map. All suggested multiple times to no avail.
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