Lead placement

Hi. I've been playing for quite a while, close to game launch, multiple accounts.... I got a question lol. I have always been performing under the assumption that when you kill the lead toon ONLY, the next toon in the lineup becomes the "lead" in the next battle attempt. For example, killing a Great Mothers lead and Ventress is the second toon in the lineup. The second battle would trigger her lead ability, correct? Or have I been living a long conspiracy lie this whole time? Haha. Genuinely curious if anyone knows for a fact.