The main carry for this comp is obviously Sion as a heavy dealer and Swain as a tank damage dealer. You will need to have 3 stars Imperials excluding Sion (2 stars), otherwise I'm not sure whether you can win the game or not. Top 4 would be probably the least at best. If you have 3 stars Imperials, there's a high chance you will win, like I did on my previous game. lol
It would be better if you have a protector emblem as an replacement for Swain's Gargoyle Stoneplate and a scrap emblem for Samira. Enabling the Scrap trait with Echo and gives you decent shields for your comp.
Level up to 6 at 3-2 round. Don't ever level up to 7 until you have Talon and Swain for 3 stars. Then at level 7, find 2 stars Sion and 3 stars Echo and Samira. Take Fiora to enable Challenger trait and also Fiora is kinda still OP even without item, as a distraction for enemies. Then level up to 8 once you have 2 stars Fiora and find Yuumi. Or Jayce for Enforcer trait as it is good for late game.