Thany. Tate's cool too, cause of HM bonuses, but using Thany makes recruiting her easier.
Dieck. Amazing supports with Clarine and Rutgar, hax bases and mehish growths. Oujay has lolwind affinity and supports with crap people, not to mention low-leveled.
Shin. Much better than Sue, in strentgh and bases, thanks to HM bonuses. The only bowman that's good in this game, except maybe Klein and arguably Igrene.
Rutgar. Gets hax crt rates when supporting Dieck and Clarine. Although, Fir is okay, but not as much 1337 as Rutgar. He is an awesome boss killer, because he defies hit and crts them all
Miledy by a lot. By the time you get Zeiss, Miledy is promoted and kicking ass, while Zeiss has to be babied, which is hard on Ilia and lolimpossible on Sacae.
Even when playing efficiently, their support triangle is still acheivable, if you keep them together a lot, espically when you're just moving up, which happens a lot in a bunch of chapters( 7x, 8 and 9A come to mind)