The "real" question that zayyeh is asking is not very real, it is more theoretical,
because the answer very possibly is gonna be something like "get 4-5-6 levels of learning, do a double boss kill at L1, take humility, double kill L9s", so not really realistic in a typical run even if you do have TT.
What is more interesting to me is this:
given the game state, and given reasonable restrictions on the strategy (only allowed +N level kills, have/dont have slow/IMAWAL/etc, disallow double kills, etc), find the optimal kill chain to max XP.
This (and the original zayyeh's question) should be doable with an exhaustive computer search, it is not that hard. It is just a pain to implement all the possibilities. Goblins (and goblin transmuters), beads, slow/wicked guitar, etc.
But even this question is not that interesting, because killing bosses is typically way easier via dings. It is only interesting to ppl who compete on top XP in the dailies or as a theoretical exercise. Personally I do not see myself doing a double boss kill on the Labyrinth any time soon
