Slot C for armor emblem

With Everyone! does stack with ward armor. Its just that ward armor grants the buff during combat, so on the outside, the unit and the ally affected by With Everyone! gains +5 Def / Res but also counting +4 from an ally with ward armor, so +9 Def / Res.

Spur-like buffs (buffs that are granted during combat such as Ward Armor) can stack while Stat boosting buffs like Fortify only go for the highest given number.

Example: Fortify Armor grants +6 Def / Res and Hone Def +3 Def. Since the +6 Def buff from Fortify Armor is greater, only the +6 is added in, while the hone is ignored.

So coming from three of your armors with Ward Armor, L! Tiki may receive +12 Def / Res if the three allies are within two spaces of her. It may also stack with With Everyone! as well, granting +18 Def / Res for her.

You could replace it for a fortify, though keep in mind With Everyone! also grants the +5 Def / Res for L! Tiki herself.

It does too stack with ward armor. Ward Armor is an in combat buff, meaning it will never be visible in their stats but it will be added in on the fly during combat.

On the other hand, Fortify Armor definitely will NOT stack with With Everyone as they are both visible buffs. Only the highest value will be applied.