It's from retail, but I and probably every other isboxer veteran can do the Darkmaster Gandling teleports with no problem, and that's as far as I remember the most complex fight in all of vanilla's dungeons for a multiboxer. The key is to have a setup so you can drive from any character and still perform the actions needed, so all you need to do is to switch to the teleported character and let the others continue on as normal while you make your way back.

In vanilla theres almost no mechanics that requires movement or splitting compared to retail and is going to make multiboxing very easy. Targeting for say polymorph without focus is going to be a bit more painful, especially mid fight, but it can be solved with manual target assignment