I did not realize, but had considered, they would make the ROF Indigo point blank. It's ridiculously good otherwise. Skill description is vague and could use some clarification.
For an ice-based caster that is a point in Blizzard's favor, but it doesn't help my sense the spell is still weak. I don't want to break theme and use Arcane Orb or something.
I also noted that a per shard blizzard has a tendency to miss against small enemies so it wouldn't always be the ideal AE. Which seems to be an argument in its favor for a unique damage mechanic. However, with Indigo being point blank and gimped I suppose it is for the best that it doesn't.
I'm also fairly certain based on Blizzard alabaster rune that cold crits do not freeze. Otherwise there is no point for them to specifically state a level 7 rune gives you a 52% chance to freeze non-crit when the function of that self-same rune virtually guarantees you will always crit. It's obviously out.
Indigo strikes me as the only end-game competitive rune.... assuming AP regenration is fairly strong if geared well. It's a roughly 2.5x multiplied and (greatly?) increases the area of effect. It does the nearly the same damage in 3 seconds that the other glyph, crimson I think, does in 10. Much burstier. Much easier to get full damage. And it hits more enemies. Alabaster at best gives you 2x damage and maybe some freeze. Golden gives you 2-4 damage for +3 ap, but base crit levels are unlikely to be good enough to make double casting competitive endgame especially if AP regen is strong anyway.