The answer is dying.
Mortal coil refers to the suffering of daily living, the chaos and confusion of life. Shuffled off means to get rid of. Therefore shuffled off this mortal coil means to die and more specifically in this soliloquy to end one's own life.
I think people think crying is a weakness because you are more vulnerable while you crying. It could also be because maybe people associate cry with babies. Crying isn’t a sign of weakness because everybody cries and it’s part of human emotions so there nothing you can do about it. Also it helps you let everything out when you’re stressed, sad angry, etc...
Since the sentence has a compound subject (he and she), the pronoun that would correct the sentence is "they". So the correct sentence would be, "Two of the best singers were they". We used the pronoun "they" instead of "them" because it is the subject of the sentence. Subject pronouns include I, you, he, she, they, we and it.
