Tuvix is the Kobayashi Maru of the Delta Quadrant.
Good way of putting it though I was personally never conflicted over the dilemma. There could be an element of "duh, of course they will be separated it's tv" at work there though.
And I don't think she would have let Lessing die. She would have risked herself to save him from the beastie at the last moment and there would have been a Trek speech about what humanity stands for.