So some time ago I was exploring possibilities of soling Yogg on not the best geared alts. As far part of you know - the boss has portal achievements. So one day I decided to leave an add behind for some kind of reason before entering brain phase. Then strange thing happened - every time when add was up (from 1st phase) and I entered the portal I got ported out so technically you could cover 100% of portals' wave each time. I don't remember if each portal can port you to different place (1 of 3) but if yes then it was / is possible to speed up this achievement.
Enjoy