The real reason. Because 10 man raids.
If they don’t do raid wide your optimal 10 man is 2 shamans, 2 druids, 1 prot warrior. 2-3 paladins. That leaves 2 dps spots open for more buffs. So probably a hunter and a rogue or a warlock and a mage.
That’s your ideal 10 man comp every time and it will do 40% more damage then not stacking that without raid wide buffs. This had to happen or 10 mans would have been horrible.
If warriors actually do 5% less single target then rogues, you will only be incentivized to bring 1 prot warrior to any 10,20, or 40 man raid.
10 and 20 man raids are the focus. They needed these changes.
Right now you can basically cover all buffs with a max of 2 of each class in a raid. This fits the 20 man really well and doesn’t reward class stacking. It helps keep gear distribution even as well.
This was the best choice to keep buffs unique to classes and work with the primary raid size focuses.