So i did some testing with raindrops made from mesh instead of displacement. Droplets was made bigger intentionally, to better see what's going on. Even without caustics it can be seen some improvement, probably that means that displacement couldn't provide enough subdivision. When caustics are turned on (again, only in material, not in caustics solver), raindrops starts to look much better at glancing angles, but i think there's too much shadowing on the droplets on front facing angles. And oh... look at the droplets on the chrome! What the...? Looks like ink, not a water :/