I would say archers are better but snipers are by far the most annoying and they're too random for my tastes. I get random shoots on my backline against archers sometimes too, but against dwarf walls it happens 90% of the times I attack them and there's nothing I can do to prevent it because so far the only pattern to prevent it that I found, will keep changing with time. It looks like there's something related with the formation you use on sieges, I can decrease the chance of getting my backline getting sniped after long tests of formations and suicide attacks but 1 lvl more on units and I need to do it all over again, so, snipers are the most annoying for me by far, but not because they're better than archers but because they're random. It's a old thing that I've been trying to understand since the game release, but now that they're stronger it's becoming a pain in the ass.
I fought some gold crossbows and while they're not useless, I would say that even Mummies are better than them, or even blasters. The reason is that they're a mix of aoe and single target as you said and in the end they can't do both in a optimal way.