"Ocoeur" is the alias of French musician Franck Zaragoza. It is, as you point out, derived from the French "au coeur". Since there is nothing on
his biog page to indicate any other pronounciation, it is most likely pronounced as the French "au coeur".
"Saycet" is alias of French musician Pierre Lefeuvre, so in the absence of anything on his fan website to indicate otherwise,
would be pronounced as a French word. Google Translate has it with a sounded final "t" : myself I'd think the final "t" is silent (as "ballet", "beignet", "Manet" etc)
Maybe the French lang forum could help out on this point.
"El Huervo" is the name used by Swedish artist Niklas Åkerblad for his musical work.
It probably dates from his involvement with the soundtrack to video shooter game "Hotline Miami".His website has many South/Central American / Latin influences, so it's safe to say that it would be pronounced as
the Spanish: "el Huervo"