Which premium A-slot skill for Adult Tiki?

If you use lightning breath+ (Res refined) then Warding Breath would be good. You can use distant counter if you use a Breath of Fog build (which is what I am working). Maximizing her res boon would be definitely effective if you have no other res based tanks, you may even be able to use Glacies/Iceberg if you choose so to. Nevertheless the skills you chose have fun building her!

I'd say merge it into another Tiki with plus defense, minus speed, and give her steady breath from BIke. Do this, and couple it with Defense forged lightning breath and QR 3 and you've got a top-tier enemy phase tank.