I'd also point out, in terms of boss mods, whether that be avre, dbm, dxe, or hwatever, we'd still be back in the days of vanilla naxx in terms of fight complexity. What boss mods do is allow Blizz to actually make more difficult, more complex boss fights.
Without the tools we have today, again, we'd be back in the stone age of raiding where there was a ton of tank and spank.