Shinon is the best marksman,Boyd is pretty top but can turn out a turd, Oscar is good but dont overlook Kieren and Astrid as Astrid can be pretty solid, Rhys is pretty neato as the only light magic user and priest, Soren's pretty aright in my experience but some would disagree, you dont NEED a tank for the end but if you want one, Gatrie it has to be, The laguz kings are must haves for the end game on harder difficulties, there is no ideal group due to the variation your characters are subject to, i once had a good Tanith better than marcia but shit's rare due to Marcia and Jill having crazy growths , Nephenee is usually a beast, devdan is cancer like nearly all pre promotes the exception to this is Titania who can make it to endgame actually decent.