Miltek

Or you can slap Hold-Out on Hortensia-Micayah. She's got one of highest speed growths in the game making her doubling most enemies even with overweighted tomes. Since she's got pretty low max HP and almost highest speed it makes her great target for Hold Out->Nosferatu abuse.

Just like most of users said, Hector Timerra is a monster, comparable to Ike builds. I've been trying Veyle Soren and it kinda works. Thanks to huge range on engage you can pull enemies from miles away while making them take more damage (Draconic Hex +Flare + Dagger Lucina), you get double crit chance on tomes and vs groups you slap Cataclysm for AoE Draconic Hex and Flame Field. It's full package and propably most *natural feeling* combo in the game (next to Diamant Ike).

Pretty much my go to. For all charracters. Ivy Celica for double Draconic Hex. Roy Alear gives him damage which he lacks for consistent oneshooting units (all through Byleth is also crazy good for 3+ to all stats instruct/dance). Micaiah went to Hortensia since her pasive makes AoE warps/freezes chance to not use charge. Plus she lacks in MAG so it's win-win situation for her. Also you can slap Hold ++ for some nasty immortality combo with Nosferatu. She's crazy fast so she wont get doubled at all. As for Leif, I put him on Timmera for one reason: sandstorm procs on each hit of Quadraple Strike hit, making it reliable oneshot for multi-bar bosses. Also she lacks BLD for silver/brave spears which Timmera lacks. Good stuff. Lucina + Marrin (wolf knight) is go to for huge rage of poison asists, plus compared to thief, wolf knight is rather tanky - making her not targeted by ranged units while Bond Shielding. As for Celiene I found that Corrin is best pick for her, simply becouse of how busted Flame Gambit/Field is (and ppl dont realise how broken it is). You've got permament, indestructable field which does slow enemy units to 1 tile per turn, while your units can shoot them down from 2-3 range then retreat with Canter. Pretty much destroys all missions where you can turtle in 3 squares wide terrain. Plus she can pack a punch with Yato thanks to non-garbage STR and Ignis.

I've got pretty much 3 skirmishes per playthrough. 1 after chapter 12, second after 18 and one randomly between 18 and 24. It didnt matter anyway coz itlf you get fliers you are pretty much dead.