Worrying about the 4-E chapters might burn you. If you level up too few units, you'll have truble in the first 6 chapters of part 4 (where your team is split up).
Among the herons, stick to Reyson. I like Leanne, so I use her, but she is quite simply inferior to him. You'll definitely want Mia over Edward for the endgame. Other than that, your team seems very fine. Far better than any team I've ever been to the endgame with, at least.
Generally, my endgame teams is something ala
Ike, Micaiah, Sothe, Sanaki, Kurthanga, Ena, Leanne, Mia, Jill, Nephenee, Edward, Rolf, Mist, Tibarn a few other random mages (I bloody love mages). I generally end up having a few useless units. On my hardmode, I had been so RNG cursed that I had to kill Deginshea with just Tibarn Rolf.
If the endgame is your problem, not using mages shouldn't be much of an issue. In E-1, mages vs non-mages isn't that important. In E-2, mages are a tad too fragile and a bit of a problem. In E-3, they're nice to have for half of the dragons. But if you bless Nosferatu for Micaiah, she can easily solo all of those. (That makes her useless on offence for the last two chapters of offence though, but she'd be bad at those anyway). In E-4. they're also bad. In E-5, they're worse than non-mages.
So, the only reason you'd want mages for the endgame is really for the healing.
Edit: Didn't see your second post. Bless Nosferatu on Micaiah, and Tibarn, Ike, Micaiah and healer should do 4-E3 easily.
