Are you using holy tanks in war?
Do you already have a solid maxed 5* tank you can use?
Cuz personally, aside from defense, I’m not all that big of fan of Guin. & As you said, you’re lacking healers, where Delilah would help you so much better in that department - and she’ll be a better addition on offense [compared to Guin] too.
Though, I may be in the minority on this, as I don’t value defense a whole lot unless war defense is also being considered [in that], cuz that’s where Guin shines the most (imo). & If you’re not using holy tanks in war, yet need a tank for defense, Delilah can still fill that role nicely.
Though, I may be bias, as I covet Delilah while already owning Guin - whom doesn’t see use outside of being placed as center in war