Hello,
My suggestion is to make a configurable option to enable the damage scaling only for certain classes.
Some classes are better at soloing instanced content on their own, like Death Knight, Paladin, Druid etc. At the same time Cloth wearing classes will struggle hard with it.
In order to create balance, it would be nice to be able to boost only the classes that struggle.
Also to avoid abuses, any stat/damage boost should be reverted if the instance is joined by another player.
I would love to hear what you think about this. Thanks for reading!