as far as i know, waterproofing is only needed for bathrooms. Other floor areas can do without. Yes, unevenness it's inevitable, it's not that a big problem. what should be of concern will be cracking, if you don't mind. A solution to this would be to ask them to lay metal strips in between to fight the expansion/contraction of cement, that's causing the cracks. Also mine was done with different cement/sand ingredients, resulting in one area giving a different finish compared to the other. That i dont mind, but should watch them closely if this matters to you.