I don't like Valla. She seems... too easy. I don't even put effort on playing her and when I check, I'm the top siege damage and hero damage from the team.
Also, I've been trying to get Jaina to lvl 10, and I was planing on buying her master skin, but now I just don't feel like playing her anymore. Ring of frost is a ultimate that more often feels like a waste, and water elemental dies too fast. She doesn't have burst damage enough to compete with other assassins and her ~keepaway~ build is meh.
She does have burst damage once you get Icy Veins, but sometimes you can't get it because of some Illidans/that kind of hero that will follow and dive you until you die, so you need to get Sprint on those cases, and sometimes even Bolt, and you lose a lot of damage because of this. Root helps, but damn, it doesn't even matter if you can't hit them/they have 30000 movement options, no resource cost and low cooldown on them.
She is pretty decent besides these things, tho.