I ended up with a rather good natured L!Lucina and immediately saw her potential with something like Galeforce Raven. To compliment these two, I chose A!Tiki for a nice tank role. Now, I am unsure on the 4th slot for the team. Given we are using Tiki, a Dragon makes for an obvious choice, so should I use: Fae, Nowi or Ninian?
Fae and Nowi would both end up with a Steady Breath build, but Ninian is using a simple Fury Dark Breath build, would probably change the breath to Water Breath.
You don't really need a dragon (don't see the logic there, unless you have breath of fog effect refined), you just need someone who can deal with blue magic reliably, because Raven can't tank at all and Lucina's mage tanking can't be considered reliable, not even talking about Tiki, who also gets destroyed by blue mages.
If you want to stick with your dragon logic, choose Fae, but there are a couple of other good choices.
Dragon is perfect to compliment A!Tiki's prf weapon, so I think Fae will be a good choice. Raven is probably not tanky enough so a green to take on enemy phase is good, and it can also covers blue threats when Tiki can't tank it (like mages as Guts mentioned).
If you think Raven can handle most of the blue threats enough, you can pick ninian as well, since you can have triple action on lucina with dance and future vision.
It's absolutely not necessary to choose a dragon unless you have the refined breath of fog, but Tiki is better off with lightning breath on this team imo. If you choose to use a dragon, Fae would work best, since she can tank blue mages and, if necessary, green mages. Otherwise you can use any other unit who can kill mages. Sothe deserves special mention, since he can target the low defenses of most mages, and buff allies within 2 spaces and debuff enemies in the same range at the same time too.
Pokemon GO
Fire Emblem Heroes
Fate Grand Order
Dragonball Legends
Dragalia Lost
IV Calc
Heroes