How come you didn’t use Hand Of Ultos? As you can take one point out of Yogul to get it for minimal downsides and instead get more RR. Although the low-ish OA this build has is slight a problem for proccing Hand of Ultos.
Build already has Viper so Ultos proc won’t bring any more RR and since there is no global lightning>cold conversion the damage won’t be good either so giving up from %100 cold damage is not an idea I would follow.
The only thing I have heard that differs between the two is that Viper has this unique bad touch with weapon damage. If it doesn’t have 100% or over weapons damage, it won’t fully and efficiently work (it depends on it) unlike ultos but then again ultos need the skill to bound on of + its lightning without conversions like ford says.