For most of my teams I use that order (AoE, HP Steal, Single Target, Multi-Hit (like triple drill or double thrust)), but I keep Canola in front because she's my hardest hitter with over 6k ATK and I want to make sure all of her damage gets used. If my AoE users don't use their skills and use single hit attacks, it sometimes results in damage being wasted if Canola needs to finish off a weakened enemy. If she's first, she always gets a full damage hit in, and then either the AoE goes off and everything dies anyway, or it doesn't go off and they use their weaker attacks to finish people off. Example of something I kept seeing which is why I switched:
Basically, it helps in the cases where the AoE doesn't trigger, and if the AoE does trigger everything is usually dying anyway. For my other teams none of the units are that much stronger than the other so I just use a normal order since there's less of an overkill problem.
I'd probably put Marigold last in that squad, since triple drill can hit different enemies and can finish off a weakened enemy and then do damage to another one (less wasted damage).