Those are Fresh 50 fights, which, you can very quickly get yourself over-geared for at this point. If everyone is overgeared for those fights, you can usually end up ignoring a lot of the mechanics, and thus can often muddle through without use of Videos.
The same cannot be said for fights like The Extreme Primals, Second Coil, or heck, even First Coil have mechanics that'll wipe the floor with if you're not careful. While it's theoretically possible to go into fights like that without watching a video, and muddle through it, in practice it's radically impractical. Even with knowing exactly what to do, these fights are huge execution checks, and often require great amounts of practice to do correctly.
Usually, if I'm running with a static group at the time, I'll go into a fight once, real fast, completely raw, mainly so I don't inadvertantly spoil any cutscenes or whatnot. However, in occasions like that, everyone in the party has no real expectation of beating that fight.
As such, I won't do that if I'm not running in a static. If I'm going with a PF group, or even a DF group, I at least read a text description of the fight first. While I hate losing that, "first time raw experience," I just can't waste other peoples time, when they really do have an expectation of clearing that fight.