It doesnt, i just did it with r7 ig11 and r7 bando. Trick is to put defence and health mods on bando to survive (around 60-70% defence at least). Timing damage immunity along with phase 1 and 3 special is crucial.
Sorry, but it did! EA already confirmed that, just read through the former post:
https://forums.ea.com/idea/swgoh-bug-reports-en/units-changed-in-journey-guide/12971613
I tried tier 1 at least 20 times with a R7 Kelleran Beq (295 speed, 147k protection, both zetas) and came not even close to winning. Other players had the same problem, as you can see.
So it's not a question of modding or gameplay. Before the update, several of my guildmates managed to do it with worse stats.
And you can't actually do much else than first attacking the veteran and afterwards the clone captain - that's how it's supposed to work.
Capital Games Team