Is it worth doing the Solas romance?
I admit, I'm curious. I wanted to romance Dorian to see what that was like... plus, none of the characters I make ever get along with him (even if they have different personalities). I can't even get my approval up enough to do his personal quest, so I guess it'd be like a challenge. Anything I say, he disapproves 
But I have issues deviating from Sera. I romanced Cass and as soon as I tapped that I went back and made a female because it just didn't feel right. It's quite sad, really. 
I've heard about that tattoo removal thing. Is it true Solas says it represents slavery, or some sh*t?
In that situation I'd be like, screw you this is part of my culture. 
Honestly, as I've said, Solas' romance is best experienced in your first playthrough. imo, it is still worth it since it fits so well with the plot.
As for what he says about the meaning behind the vallaslin, well, he basically says that it does represent the Creators, but it was mostly worn by slaves, and the designs were determined by which Creator the noble they served worshiped.
Honestly, though, I don't think that what he considers slavery is the same as the slavery we think of (Tevinter-style slavery). Especially considering how the Sentinels (who obviously didn't serve anyone other than Mythal) wore vallaslin themselves. But this is a discussion for somewhere else.
As for Dorian, I have to actually try to get disapproval with him, otherwise he'll be my best buddy. Same goes with pretty much everyone except Vivienne and Sera, but only late-game for Sera. But then, I'm very pro-mage and I always end up getting a ton of Friendship with Fenris in DA2, so maybe that's a moot point.