I’ve just finished my trooper team and I would say you need snow for damage, very important against NS. Stark provides essential turn meter and buffs for damage. Death trooper is very good for the raid, works well in other raid teams but farm is quite long so up to you. Finally you want shore or storm for the tank. Shore is definitely the better character however is harder to gear and the grind for shards is painful. I stopped farming him once I unlocked him at 3* because it was taking too long for me. Go for storm if you want a full 7* team.