I very much agree here. An evil race is indeed not a Sanderson-thing to do, as he tends to create much more three-dimensional worlds. Of course, there are (original Mistborn trilogy spoiler)
while the Listeners, I am pretty sure, have not been created by Odium. I cannot actually find a source for that, but it is both logical (they're clearly sentient, and Odium would most likely not give up power for that) and I do believe I've read Sanderson confirming it just this week (though in an older interview).
This is also an idea that I really like. According to the coppermind page, spren are "powers of creation" (https://coppermind.net/wiki/Spren), which gained sentience due to human intervention. This would imply that they are not directly created by Honor and Cultivation, and have merely gained their characteristics over time because Honor and Cultivation were around. Odium, however, has also been around - so maybe, we should not be looking at a line, but instead a triangle, where sprens can be at a corner (100% influenced by one Shard), a line (influenced by only two Shards) or somewhere on the inside (influenced by all three shards). Hope that makes sense to everyone, but otherwise I'm happy to clarify.
EDIT: To expand upon this, I came across a question asked to Brandon before the release of WoR (http://www.theoryland.com/intvmain.php?i=747#5), which says that all the spren we are running into (but only in the first and maybe second book) are of Honor and Cultivation. I'm not sure wheter this is intentional or not, but Brandon is excluding later spren, which might include spren that are part Odium and part Honor/Cultivation.