You have this the wrong way. Addons/WAs are not needed because the boss design is crap. The bosses are designed this way because addons and WAs exist.
Blizzard has talked about this a few times already. It’s an arms race between raid encounter design and addon developers.
Blizzard is designing bosses with addons and WAs in mind because if they’d ignore them, the encounters would be far too easy with them.