I hope 2 months-ish isn't too much of a necro, but this is one of the top threads that keeps popping up on google when I search for answers.
Now that all the DLC is out in the states (or the very least, you have access to one of every class medal by now) I'm curious what people have found to be helpful?
In my Conquest game, here's what I thought worked out well:
Dread Fighter = Odin, this required a LOT more effort on my part and an arms scroll or two to make functional, however once it was Odin tore things up with a mixture of Strength and Magic weapons. I'm sure there are better candidates though.
Lodetsar = Laslow for sure.
Great Lord = Peri, for me I had an excess of mounted units and I didn't see the point of having a 5th mounted unit with Peri. If by chance you're S-Supporting her with Laslow they make an extremely deadly blue-caped combo, especially with the "Dual Guard" skills the classes have.
Vanguard = Arthur, definitely Arthur. Just being able to still use Axes was a great boon. I used some of the other scrolls on characters like Xander and Selena.
Grandmaster - Leo, not only does it fit his character's personality, it also trades his mount weakness for a higher cap on some of his more desired stats, the only tradeoff is a little more squishiness.
Dark Flier - Yozu, I went straight to making her a Dark Flier at 10, because of her already crazy stat growths she became a pretty versatile air unit for a majority of my early game.
I have no input on Balistician or Witch. I'd probably make Nyx or Elise a witch, maybe Ophelia, and for Balistician I'd probably make Anna one or Shuma or something.