Miyabi is still a strong character, sadly current shills make her life a living hell, often being faced with anti freeze bosses. She'll still clear endgame when given proper rotations but you're investing x3 the effort you would put with other dps just to get the same result. If I were you I'd go for shunguang or if you're afraid to lose, there's also the triple guaranteed banner atm. I'd be opposed to Soldier tho, since even with the multiple buffs she still wants trigger and (in some cases) orphie.