#1 - Feb. 11, 2017, 11:15 p.m.
Frost plays really well at the moment. The hotfix to Brain Freeze made the rotation much smoother and generally more fun (thanks to Frostbolt/Ebonbolt combo being viable/optimal way to use Brain Freeze). I actually like that Flurry isn't "whack-a-mole" style of proc that you just use when the button lights up. The cooldown reduction on Frozen Orb also makes AoE more fun and satisfying.
However, there are still a few problems.
Travel time and impact timing
Frostbolt and Ebonbolt still need some distance between you and your target (about 10 yd for Frostbolt, 13 yd for Ebonbolt) for the followup Flurry to shatter them. While much better than the previous 23 yd, this is still not ideal.
Similarly, the followup Ice Lance only does full damage if your GCD is 1.4 s or lower, with the timing being more strict the further you stand. And on the other hand, if you're standing very close (or even running towards your target), it's possible to fit two Ice Lances into a single Winter's Chill if your GCD is short enough.
Some possible solutions are at the very end of this post.
Water Jet
I like that Water Jet requires some thought to get the most out of it, but it's nearly impossible to use properly at very long distances or high haste. At that point, the travel time of Frostbolt becomes the deciding factor of getting two Fingers of Frost out of a single Water Jet. You can see a lot of mages switching to Lonely Winter for Krosus mostly because Water Jet stops reliably giving you both charges.
One possible way to fix this is to give Water Jet more room for error. For example, increase its duration by 50% but limit it to only generating two charges of Fingers of Frost.
Proc management
Brain Freeze hotfix solved one of the major gameplay warts, but proc handling is still not perfect. Some Fingers of Frost charges are wasted simply because they happen right around Brain Freeze Flurry and the mage cannot react to them. Simple example is casting Frostbolt, Brain Freeze Flurry and Ice Lance - this sequence has 12% (16.8% with Frozen Touch) of wasting Fingers of Frost charge. This also happens when the FoF comes from a different source (active Frozen Orb, legendary gloves - though the latter can be played around and offers some gameplay depth).
I'm not sure what the proper solution to this problem is, because simply refunding the Fingers of Frost charge would probably be too powerful. Perhaps a simple bonus to Ice Lance damage - not enough to make the mage go out of their way to launch Fingers of Frost Ice Lances into Winter's Chill, but enough to make the Fingers of Frost charge not completely wasted.