Young buck was his only real genuine discovery you can argue that he was able to see the talent in game, because he agreed to work with him but game was dr dre's discovery technically. Everything else was signing dudes who had previous success on some level like shawty lo, m.o.p and mobb deep or just can't cut it or have dated style of music.
Olivia could actually sing though, that actually had a shot of becoming a lot more than it was. Not to say she was going to be mariah carey or some s*** but she could have sold a couple gold albums at least but her career push was framed around a rap group which basically buried her chances.
He almost signed uncle murder and this latest chick he signed is like some sort of carbon copy of 90's female rappers.
In conclusion yes he does not really have the best taste, not every rapper is cut out to be a music exec lots of rappers started labels that went no where, wu-tang was one of the first, missy elliot had a label, hell who didn't or doesn't have a rap label and of those labels that have been somewhat successful they have only had a couple acts that really been successful.