"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".
Edit: 25th August 2020 : for 'Saycet' answer to correct/amend my own answer and include additional information provided in answer by @Bebs (thanks!): "Saycet" is an alias of French musician Pierre Lefeuvre and his collaborators. His fan website gives no clue as to the pronunciation, so I as a non-native French speaker assumed the final "t" is silent (like "ballet", "beignet", "Manet" etc). However, Google Translate has it with a sounded final "t" : as do the 2 interviews in @Bebs' answer : interview 1 interview 2- so the "c" is soft and the final "t" is sounded.
"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 Spanish: "el Huervo"