Honestly I think having an offensive caster AND a healer is not neccessary in the slightest. Offensive symbols really kinda suck, so I'd just pick one symbologist for healing and have either three melee's, or two melee's and Reimi.
For Melee, obviously Edge and Meracle are the best choices, followed by Arumat (and turn off those pesky symbols, they suck!).
As for your healer, a LOT of people are gonna tell you to use Sarah, because she gets this or that symbol. But I say screw all that, and use either Myuria or Lymle (I prefer Myuria for.....certain reasons...) because Sarah can't learn Fast Cast, which is pwn.
My A-Team is Edge, Meracle, Arumat, and Myuria. And I luvs them muches.
Oh, I meant to mention (and forgot) that in order for Myuria or Lymle to outclass Sarah as a healer you need to get the Faerie Star manual from the Trial of Wisdom quest and teach it to them. THEN they pwn.
In close range combat =================== Meracle has the highest damage, even more than Arumat. She has less HP and def which makes her die pretty often if you let AI controls her. Her combo deals INSANE damage especially to one target. One of the few characters that you can solo a boss with.
Edge is the best meat tanker for melee fighter, and his move wasn't... THAT BAD. He works really well in post game dungeon where you most of the time controls range fighter or healer and let AI run in to buy sometime. His damage potential is less than Arumat and Meracle, but he trade that with his ability to stay alive longer even if you do not control him.
Arumat is the master of LOLSPAM. His special is totally broken and can be spam VERY easily. Has less def and HP than Edge, but more than Meracle. I personally use him more than the other 2.
Range =================== Reimi is the CRIT god. Her damage is extremely high since she has the highest crit modifier in the game. Her special does multiple hits attacks and FFFFFFFFFFFFFFF for awesome damage. She is very easy to control as well.
Bulucus deals less damage to a single target than Reimi, but his BlackHole put him in a different light. He can spam nice AOE damage to multiple targets and controls the whole battle field with ease. He also has insane amount of HP and move really fast too.
Spell Caster =================== There aren't any good one in the game...... all spell casters are better off healing. I am not kidding here.
Healer ==================== Myule (or however you spell her name) - spell does so little damage in later game, so I won't go into that. But heck she CAN HEAL!! She even can learn the best healing spell in the game (90% heal all party!!) Whats put her an edge over Sarah is that she can FAST CAST!!
Lymle is the same as above, I sometimes find her special more useful since it knock energy off ground. If you can stand her VA then...
Sarah - THE HEALER of the game. She comes with early heal spell and can Rez chars to 100% heath: she is the only character that can do this. Down side.. is she can't fast cast. Thus she cast slower than the other 2 mages.