I think an important thing to keep in mind with singleton breaking is that you can always just, adjust the numbers. I like to start at 2, bump up to 3 if something feels really essential. But you can also start at 4, bump up or down if necessary. It can feel intimidating if you've never done it before, but it's really no different from adjusting the density of any other effect! We do this kind of adjustment and tuning with things like removal density, creature density, counterspell density, whatever. It's no different just because it's extra copies of the same card