From the beginning, my problem with Henry Cavill was that he is too neatly and delicately handsome. He is too handsome. Muscle is not enough to create a tank look. I don't know the Witcher in the books, but to me, the one in the game is too neat looking too. No body hair, a delicate, small unbroken nose, clean appearance... When my mind is given this kind of material, my imagination insists on a really shabby, dirty, hairy, rough-tough character. He is an outdoor living warrior. Anyway, it works. The voice works. Bigger nose. Voice affects me a lot, it is incredibly important and I think he made it. I wouldn't be surprised if they checked first the voice while casting. Overall, It wasn't as bad as I thought, it was good. My fear is that as the series develop, they are going to make him more neat and clean.
About that particular light and the quality of shiny cosplay feel is that I think it is on purpose. I think they didn't want to give a realistic, darker, historical feel, but a game and fairy tale come true feel. It feels like they are aiming for more Merlin than Game of Thrones. Strategically it is a clever move in my opinion. It is more 'sincere'. Especially, because it is released after GoT. People are still talking about it. For example, if they created the massacre of Cintra in the scale and detailing of the burning of the King's Landing: it wouldn't fit the whole, it would be too epic for a first season first episodes; unbalanced in these two senses. It would remind a very successful, very highly hyped just ended series. And those scenes in Got is in the last season, it is even final there.
About the eye make up, I don't think the problem is that it is just badly done. They are good. This is a general proıblem in movie industry with traditional make up or cgi. Yes they can blend it now much better, but the problem is that there are no human eye colours of the sort in reality and eyes are very highly expressive. Our minds have no reference points for these eye colours and their expressions, we don't know what/how to match yellow or purple eyes with some expression in reality. How does a pair of yellow eyes differ in giving an expression of anger or resentment? Purple is obviously easier than bright yellow, so Yen's eyes look better. They tried to give a sense of natural, changing in light look to her eyes, but you'll see this time people will complain that her eyes are different colours in some scenes.