Extremely important difference here is WoW has had addons since forever, it's always been compatible with them. And starting around Wrath of the Lich King nearly everyone had Deadly Boss Mods which Ion has said he now designs around since top guilds will of course have DBM.
In other words WoW's encounters are designed with DBM in mind (doable without but much more doable with). That sort of thing will never happen here.