..and what is worse, then?
Janna, Nami, Bard should always be given IMHO. NOT because they're bad champs - but because they're all utility based champs which by default makes it harder to carry the team. There literally are no bad champs in this game, and even the worst winrate champs (Nunu, Kalista, Azir, Tahm and Nidalee right now) are extremely threatening in the hands of a skilled player. Give, for example, those 5 to a skilled team and you'd see how much of a horror they can be.
Nemesis draft is, just like any other game mode, a comparison of skill of the players. A good Janna will smash Azir, but the same applies to a good Azir - the only difference is that Janna will have more trouble applying her advantage to win. So, it makes a lot of sense to stuff utility champs to the enemy team in order to make it harder for them to carry.
Feel free to post your list of champs for Nemesis if you disagree and you think that there are champs so bad that even in good hands they're worse than utility ones.