It looks "easy" but .... maaaaan I've spent ~2 hours to clear this stage. The mechanics from event Stultifera Navis felt completely unfair. (certain units being unblockable on that "puddle", stunning your ops ) I am surprised that Alt Eya with no mods/buffs is actually (no ATK+ and no SP+! on her) enough to prevent your ops from being stunned and to heal enough. Because I had that issue an op getting stunned then a leak or more of them happens. I had very similar setup. With Horn just below Typhoon to help with damage. Still had 2 leaks with block 5 Saria in place of your Mudrock. Is 20 attack speed not worth the loss of +20% ATK on guard operators?
indeed it looks "easy". it was all about RNG of what starting operator you'd get Another way to block the puddle is to have 2 layer of ground unit. this will limit the puddle to the frontline units only eyja2 by far is the best Wandering Medic. Alternative to her would be Lumen S3. Guards are not recommended aside from SilverAsh, Mlynar and Lappland. they're good for blocking some special skill of enemies, along with emergency crowd control Saria's can only do one target at a time compared to Mudrock's S2, hence I generally have vanguard's buff on her so her S2 will be always charged and ready Often I'd go for aspd instead of atk buff, as they often 'solves' crowded enemies