I put my counter team as my healper team for this week to let you test it by yourself.
Equipement bonuses count a lot yes. That's why event girls are so good for counter teams. About your girls, you can clearly replace Fire Lily and Rose.
Fire Lily has only a tiny 80% of 2.2xDEF counter. Just slightly better than event girls but without full unlocked equip slots. This girl is just a boss killer. counter is a little bonus but it's not enought to give her a solid place in a counter team.
Rose has a nice 100% 3xDEF counter with healing skill but her defense is a shame and her solar gauge ability don't help at all on raid bosses or harder missions were strong counter is needed.

I don't know if you have Echeveria but if you have her, she is a good option too, like Mountain Lily. At least as placeholder before Tartarian Aster.

And about 2 gold equip. flowers, if you mean gold dressbloom, give them to Pink Miko. imho it's the best way to spend them since she is the girl with the highest counter rate.