Hmmm edward might be a bit too troublesome to train effeciently in hard mode, take nolan instead from the dawn brigade. He has very good gains,he is powerful and has the nihil skill which is very usefull against the dragon king and ashera plus his element is earth which is the best in the game. If you like myrmidons take mia and give her alondite or/and zihark which also has the excellent earth affinity, pair them and they will avoid everything and tear apart enemies in the process since they activate criticals and astrum regularly.
The laguz royals are all great so you can't go wrong there and the others your thinking about like elincia shinon haar nephnee are all great so no problems there. Also consider gatrie if you like generals and boyd for pure power is good too.
For herons reyson is good but i prefare rafiel since he can vigor 4 characters straight away without having to transform, just stick tormod's celerity skill on him and you will be good to go ;)
