A druid would round out your party nicely, especially as you already have ample mages and tanks. An extra healer/tank i.e Jaheira would go well with your group, if she is dead and you have no intention of resurrecting her then Cernd might be the way to go. IMO, a character with druid abilities should always be with the party, to help out with support/healing spells and to counterbalance your cleric, or half-cleric since its Aerie
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If you dont want a druid, or feel a healer is unnecessary-then Mazzy/Valygar is the way to go.I wouldnt recommend Edwin as you already have enough mages and
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*spoiler* Minsc and Edwin do not get on. Eventually they will fight each othr and you will lose one. Besides Edwin is a A$$hole anyway
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Who you chose out of Mazzy and Valygar depends-to a certain extent-on the weopon proficiencies you have given your PC and NPCs. Hope that helps.