If I only like 2-3 hairstyles on my characters, that's 2-3 times I can cheerily replay a game, because for me, using the same hairstyle across characters becomes irksome...
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I know there are people out there who are talented enough to create huge disparities in the facial structures of characters, that even with the same hairstyles, they look dissimilar. I am not one of those people.
I'll start this by saying that I'm not a great wiz with the CC, and I also agree that many of the DAI hairstyles leave much to be desired (in addition to the texture, only somewhat better than the default Skyrim hair).
That said, there are a lot of hairstyles. Also, DAI has something that DAO and DA2 did not have, which is allowing hairstyles to be available to both genders. That alone is a boon. The options are there, we just don't like them. They can't do anything about that. There are a TON of DAO hair mods; an astounding variety. I dislike about 80% of those hairs, but that does not reduce the actual variety that exists.
As you said, there are really talented players that can do wonders with the CC. You or I not being one of them isn't really something that Bioware can do anything about. We don't have the capability to use the CC to its full potential and that is our failing. BUT, I will say that this particular problem would be mitigated with face codes, or even just numbers next to all of the CC options (complete with x,y coords for the boxes) that would allow us to more accurately copy another player's settings.
Unfortunately, slider settings and face codes was something requested numerous times in multiple threads during DA2 and during DAI development. It wasn't implemented. Whether that is because of a limitation with the Frostbite engine, lack of resources, or because the devs just weren't interested in adding this feature we will never know.