For sure, but since you started adding pronunciation guides, the topic is fair game I figure.
I think one key aspect of pronunciation is that most names will vary depending on what your country of perspective is. Roman names like Hercules and Nero will be pronounced completely differently in English and Danish (which is my mother tongue) even though they are the same name. And presumably nobody knows how they were pronounced in ancient Rome.
To me, the first youtube video you linked sounds like an English pronunciation, whereas the second sounds to me like a Greek pronunciation.
Which one is "correct"? Even though the language of origin is Greek, I would lean towards the English as the default pronunciation. Because Arena Rex is written in English and I therefore assume most people would be speaking English to each other when playing. When I play with my New Zealandish friend, we speak English and I will say "Nee-row". When I play with my Danish friend, we speak Danish and I say "Neh-roh". Where both are Nero the bull, and both are correct for the respective language, assuming he is pronounced the same as the Roman emperor.