I think you're going to "miss" content regardless. Like if you play as a druid you'll get extra content like dialogue in the grove. If you play as a githyanki you'll get extra content due to how you're treated. Same I think with drow and dragonborn.
So personally I don't think about it because I'm going to "miss" content regardless of whether or not I play as a Tav, dark urge, or one of the origin characters.
Yes, but the point of contention is that it looks like you will miss *more* if you play Tav vs any other Origin/Dark Urge. In regards to your Gith example, you could roll a Female Githyanki Fighter, and the biggest difference you'd notice between your Gith Tav's playthrough and playing as Lae'zel would be a marked lesser degree of story and content.