Infinitely better is a stretch. Shiho's big claim to fame is that she has aggressive stats for her class and a pretty hefty multiplier when you've got her skill maxed out. She definitely beats out Kagura on throughput but you need to 5/5 her for the difference to become dramatic meanwhile Kagura was an easy to perfect star unit and breaks about even in terms of AW ability. If Kagura's skill was any worse I'd be right there with you in trashing her but ultimately an attack speed increase skill is pretty acceptable on a unit who will be using that time to heal anyway.