It's mostly just set up that way because my team lacks a Reduce Damage from pests. The back 4 don't particularly matter but with my alt account using my main account as the primary helper when it runs 12-5, my Main Account's squad storms ahead and takes almost all damage from the map in the form of Small Pests. The team used to have more AoE with Conva as the mage, but I got in the habit of moving Alpinia to the first unit from the back line to help my alt grind 12-5 runs easier.
My alt's teams 3-4 hover around the same speed as my main account's helper squad so they've occasionally pass Alpinia&Co. and get killed off at the first Threestepper. I found that leaving Alpinia first gave her more chances to proc a heal, because for a while my alt's girls were all lvl40 or so and Alpinia was able to solo the Queen Bee only if she went in with more than 20% health. Early on it made a notable difference in the suitability of Alpinia due to her gear slots.

Most of that is out the window with tomorrow's rewards and the last week of grinding on my alt though. I was hoping to change my squad order today/tomorrow with the rewards and tomorrow's yellow Dragons to evolve Daisy but... Maintenance. #BlameNameless

But I appreciate the advice Myrdin! I really should optimise that asap.

Edit: Life Gems for Dressblooms and better Dragon odds, as Maladaptive said, would be great QoL improvements.