I think that it is the “each and every” reading @Gene offers that informs the occasional usage of 諸 as “all” (although I can’t find an example of it specifically translating ‘sarva’ atm).
Consider T1564.23c16 Madhyamakaśāstra @
All Buddhas either speak of self or speak of no self. All dharmas’ true aspect, within this, there is neither self nor no self. All dharmas’ true aspect is defined as mental activity’s and spoken language’s ending. There is no arising and no cessation, there is calm extinction, such is nirvāṇa. All is real, all is unreal, all is both real and unreal, all is neither real nor unreal: this is called all Buddhas’ dharma.
Notice how 諸佛 & 諸法 are used in the above at opening of the 1st and 3rd lines. Interestingly enough, and this is IMO, we lack a Sanskritic recension that would give us exactly what the Chinese is translating here because, once again IMO, the Madhyamakaśāstra likely comes from a nonstandard, minority, or divergent recension than the Sanskritic MMK we all know.
Although you’ll likely note that Charles Muller, who the DDB entry is based on, doesn’t actually cite any sūtrāṇi for that entry.
Consider T1796.635a22 Mahāprajñāpāramitopadeśa**: 不染著諸法三昧
To contextualise how 諸法 is being read in T1796**, from later in that same 18th parivarta 399a21**: 月幢相三昧者，如大軍將幢以寶作月像，見此幢相，人皆隨從；菩薩入是三昧中，諸法通達無礙，皆悉隨從。
**EDIT: I mistakenly referred to T1796 as Mahāprajñāpāramitopadeśa above. I misidentified it as the upadeśa by accident. T1796 is a commentary on the Sūtra of Mahāvairocana’s Completion of Buddhahood. The rest of the citations were supposed to clarify 不染著諸法三昧. Instead they are free-flowing examples.
The rest of the citations are from the miscellany (parivarta 18) of T1509, the real Mahāprajñāpāramitopadeśa:
709c29: […] 如諸法實相之音『有佛無佛，一切法、一切法相空，空中無有相，無相中則無作』<-- this uses both 諸 & 一切, but there may be a nuance I am missing in the text. I am only an amateur Chinese language enthusiast and am far from being able to immediately look at these texts and read a cogent string of sentences.
Observe later in the same 18th parivarta again