Well, in terms of official/professional translations, it seems this phrase has already been translated in many different ways. In both Spanish and Estonian I found two types: those that translate "the mass of men" literally as a "mass" (which is a cognate in both languages) and those that interpret it as "the majority of men" (or sometimes "almost all men"). And within those two types, another two types: those that translate "men" as "people" and those that translate it as "male people" (men as opposed to women). Which gives at least four interpretations from which to choose....
I'm going with "the majority of people" for Spanish, Estonian, and Võro. Giving Votic a try as well.
The mass of men lead lives of quiet desperation.
Die Masse der Menschen führt ein Leben in stummer Verzweiflung.
Mae'r mwyafrif o ddynion yn byw bywyd llawn anobaith tawel.
Tá saol éadóchais chiúin ag an mórchuid daoine.
La mayoría de las personas llevan vidas de silenciosa desesperación.
Le masse degli uomini conducono vite di quieta disperazione.
La mòtera di omegn vif vites de acorta disperazion.
Suuri joukko ihmisiä elää elämäänsä hiljaisessa epätoivossa.
Enamik inimesi elab vaikse meeleheite elu.
Inämbjago inemiisi eläs vagadsõ meelehiitmise elo.
Suurõp ulkk ihnemiziit eläb ommaa elloa iľľass tuzgass.
대부분의 사람들은 많은 것을 포기하고 살아간다.
芸芸眾生苟活于平静之絕望中。