There's a TL;DR at the bottom of this post.
Right now, I think the biggest problems that actively make the rotation less enjoyable are Flurry and Water Jet.
Water Jet
Water Jet is an awkward spell, the main problem comes from the fact that WJ has no travel time, while Frostbolt has and is rather slow. You have to adjust for distance to target, your target's hitbox (using WJ on bosses the size of Kromog is especially annoying) and your haste. While Icy Veins and Time Warp are up, it's nearly impossible to get 2 FoF charges out of WJ unless you're standing in melee range - Frostbolt can travel for up to ~1.5 sec while WJ lasts 1.7 sec.
Adding travel time to Water Jet doesn't really solve anything, it just moves the problem into pet micromanagement (you have to adjust for pet position instead). Instead, I think Water Jet should last 50% longer and only generate up to 2 FoF charges (to allow for more room for error).
Also, for some reason Water Jet is not affected by Rune of Power and Incanter's Flow while Waterbolt is.
Flurry
Flurry also exposes some problems related to travel time. Currently, if you have less than roughly 3000 haste, Flurry into Ice Lance stops working at max range and the less haste you have, the smaller the distance from which it works. Flurry into Ice Lance should just work on all gear levels.
The other problem is the Flurry combo (Frostbolt -> Flurry -> Ice Lance). For talent setups that seek to abuse Chain Reaction the combo can add around 10% extra crit to Frostbolt which in turn leads to about 5% overall DPS increase. Now, I don't have a problem with the combo itself (it's actually fairly interesting interaction), the actual problem is that you need to stand far enough for it to work.
Either the combo should be broken (doesn't work at any range/is DPS negative) or made consistent (works at all/most ranges). Losing up to 5% of your DPS because you stood slightly too close or the encounter didn't allow you to stand far from the boss is just silly.
Those are two main problems for me, there are other smaller problems or wishes that I think would lead to better gameplay.
Baseline AoE
Baseline AoE is just bad. We need to pick up every possible AoE talent to fix it. Blizzard cannot really be buffed much more because then it will just creep into ST rotation (which should be reserved for Arctic Gale).
However, Frozen Orb does not have such constraints. Blizzard could once again reduce the remaining CD of Frozen Orb upon dealing damage and Frozen Orb could do more damage (to feel more like an actual cooldown). This not only fixes baseline AoE damage (and makes Orbital Strike trait not completely worthless), but also leads to more engaging gameplay.
To keep Blizzard from ST rotation, the passive could be restricted to Blizzard hitting 2 or more targets or maybe just make the reduction work for each target hit and tune the numbers accordingly.
Boring spells
There are also some spells that are useless or don't feel like a cooldown at all. Frozen Orb has already been mentioned above. Ebonbolt is basically the same thing, except it doesn't have the niche of being also AoE spell. Ebonbolt really needs something unique to differentiate it from Frozen Orb.
Cone of Cold is another spell I miss a lot. The slow is sometimes useful, but right now, it's barely worth a keybind. I think Cone of Cold could be used to make AoE more engaging, either some interaction with Blizzard/Frozen Orb or just flat damage buff (150-200% sp coefficient should make sure it's worth using but also isn't too strong to force yet another mage spec into melee range to do AoE).
Chain Reaction
Other minor issues relating to artifact and talents. Chain Reaction is too strong. This wouldn't necessarily a bad thing, but the trigger condition is too restrictive and has weird effects on our rotation. The Flurry combo is one example (where the damage loss from Brain Freeze proc munching is far, far outweighed by the gain to Chain Reaction uptime). Another example from personal experience: after getting the Ice Lance bracers, not using lvl 90 talent is a dps gain over both Frost Bomb and Arctic Gale simply because casting more Frostbolts leads to higher Chain Reaction uptime that makes up for the lost damage. Basically, it's a trait that punishes us for not casting a filler spell.
Other talents and traits
Orbital Strike is next to useless, but this was addressed in the Frozen Orb section.
Lonely Winter is in a better place now. I'm not sure if it's just my particular gear, but I've been finding LW setups in the top 20 talent setups (out of 243 possible, not counting level 30 and 75 tiers).
There are also two talents that add extra charges to our spells (Ice Ward and Cold Snap). I think they should also reduce the cooldown of the affected spells to make them more useful. Cold Snap is especially bad in that regard, as full recharge takes whole 10 minutes.
TL;DR
- Increase duration of Water Jet by 50% to give more room for error
- Fix Flurry so that Flurry into Ice Lance works at all haste levels
- Remove the weird positional requirement on Flurry combo
- Reduce dependency on AoE talents by buffing baseline AoE
- Make Ebonbolt and Frozen Orb feel more like cooldowns
- Buff Cone of Cold so that it isn't dead useless
- Chain Reaction shouldn't punish casting non-filler spells