I really like Ray of Frost and would like to see it get some more support, while maintaining it’s unique niche. Unlike the other two wizard channeled spells, Disintegrate and Arcane Torrent, Ray of Frost doesn’t pierce by default. You have to burn through the nearest enemy in order to hit anything behind it.
Light of Grace makes Ray of Frost pierce, but that just makes it into a clone of Disintegrate, which isn’t very interesting.
When Light of Grace was originally created, there was no downside to it, but then Ray of Frost was changed to have a small splash radius around the enemy hit. That opens the opportunity for a more interesting legendary: one that increases the splash radius of Ray of Frost. You still preserve the unique nature of Ray of Frost, in having to burn through nearby enemies to target others behind them, but it would still mitigate the primary weakness of Ray of Frost and make it more viable as a primary form of DPS.
This also has the advantage of being exceedingly easy to implement. No new graphics or effects would need to be implemented; just modify the number controlling the radius. 5-10 extra yards would probably be enough to be interesting (along with a damage boost to the skill). Or, have it do half damage to everything in a much larger radius, to preserve some of Ray of Frost’s uniqueness as a strong single target channel.
It would probably make sense to have the item affect Sleet Storm differently, since it already has a much larger radius. The easiest route would be to simply have it not affect Sleet Storm at all. More complicated about be to make the item allow you to move while channeling Sleet Storm, but increase the splash radius for other runes. Since Sleet Storm does less damage, that would allow the item to support both a speed variant and a pushing variant of the same build; you use Sleet Storm for speeds and Ray of Frost otherwise.
If included as part of an intended build for a 6pc set, I would want to see Ray of Frost as the primary source of damage. We already have a number of builds implemented around Etched Sigil, and Etched Sigil encourages channeling for brief bursts; I’d like a set that rewards extended channeling of non-Sleet Storm rays of frost.