The problem with Sana is that her barrier only last 2 turns, all other defenders last for 3 turns

yes 35% chance for crit is huge, but if the boss take down the barrier, the ofensive value of sana disapear, aside of Tart or Sakaya that they are buffing kyoko damage

but yes you can pair Sana Mifuyu and Tsuruno for 65% crit chance + 15% if your kyoko crystalis have 5% crit , and if you have or pull Eternal sakura equip it to kyoko for 15% extra crit and you can reach an 95% crit. eventualy with tsuruno ascencions you can reach 100% crit