I swear people, do you even know what an Est is?
Neither Donnel nor any of the Dawn Brigade are Ests because they don't join in the lategame. The only "Ests" in RD are Pelleas and maybe Sanaki. I'd argue that the children in FE13 could be considered Ests(especially if you don't grind for supports).
I saw Kurthnaga as an Est-character to though. I liked training him, Pelleas and Sanaki to.
Used Est herself in FE11 a lot to, cause she joins in a map with an Arena where she can win quite easily. Also the Ridersbane is useful in that chapter to get some kills. Most of your real fighting units take too little exp anyway from the Cavaliers on that map, and should 'hunt' for the Paladins to get exp. I never could use her in FE12 though. Catria, Palla and Shiida 2 gewd (and you also have to use Minerva for End Game ****).
Nino is a very popular Est. But without Alfa Drops I'm not using her. She's good though, if finally caught up. Still, I don't really need Sages in FE7. Lucius and Canas are enough for my Magic team, and Pricilla is mostly the healer. Athos does all things, and if I find myself wanting another Mage, I'd opt for Pent earlier. Pent is cool, being a noble and not giving a damn, just studying magic in the desert with his wife and an old hippie friend (Athos is cooler this way, trust me).
'And then like... The Dragon came man, and they like, changed form into humans man.' 'Nergal was always bad tripping man, couldn't handle the Dragon stash dude I tell you.'
Other Ests I used? Not sure.