unless a set has conflicting conversion it might be fine,
in this case it’s more about bonus/flavour conversion being lost to one side, while perhaps not really being that necesssary for the side gaining it.
Unfortunately Z did say the game isnt’ and wont be balanced around DD builds, and double dmg sets is more about offering 2 different build options than a 50/50% hybrid split dmg build 
Until the new change lands(unless i misunderstood the other changes), i think you can still probably do a double dmg SS, as long as you no longer use reaver’s amulet to do it.
DD omen, so far atleast, also rather still doable, but with global conversion change you will be locked in to shards of asterkarn/gravetouch for split dmg devils/totems etc, in theory should be doable.
Non devil/omen/SS double dmg melee AA reaper/trickster will probably be whatever since so many conversion slots are blocked anyway, it probably really shined more full swinging either side even if that wasn’t even top (not counting the green monster reaper that got morgo nerfed back in the day)
For Dags, speculating on the change, it should be 0 impact if it was, the conversion just shifted slot, so if you use both fire+lightning gun you still get split conversion as before
*remains to be seen if understood those changes correct ofc
Radagan also technically didn’t lose acid dmg to conversion, it’s just that acid->vit conversion isn’t exactly easy to do with it, so flat dmg mod changing from vit to acid changes the split.
But with the overall set changes, steering that much to acid for kalastor/DE, and spam Sigil being gone/sigils can’t carry and unsure how you would split DE or RoK, that might be a bit more up in the air whether double dmg potential is “gone” there or just harder. Tho that was probably hardly ever “competitive” to begin with there and required even more tolerance than usual off meta metrics (tho probably because of sigil dmg and not purely split dmg)