Arcane has 8 Legendary items to choose from. I thought I'd make a thread for us to discuss the uses of these legendaries in more depth.
To start, I'll post the rankings from Altered Time. They're not comprehensive.
For ST:
AOE isn't available yet. I'll update when they are.
Arcane-exclusive legendaries:
1) Mystic Kilt Of The Runemaster: Arcane Barrage grants you 4% of your maximum mana per Arcane Charge spent.
Pretty great. Basically allows you to extend your burst phases for longer post-Evocation (by maintaining quickening). Also allows you to have mini-bursts in between.
2) Rhonin's Assaulting Armwraps: Arcane Missiles has a 10% chance to make your next Arcane Blast cast within 5 sec cost no mana.
The best one according to simulations. This is because it has a chance to proc on every individual missile of Arcane Missiles.
Regular Arcane Missiles has a (1-0.9^5) = 40% chance to proc this
Rule of Threes Arcane Missiles has a (1-0.9^8) = 57% chance to proc this
On average (33% chance for Rule of Threes ~= 1 per 3 casts) = (1-0.9^6) = 47% chance.
That's huge. That means on average you have almost a 50% chance to get a free Arcane Blast every time you cast Arcane Missiles.
Considering that AM proc relics (Ethereal sensitivity) are BiS http://i.imgur.com/USo2rtS.png, that means you should have (15+6)*2 = 42% chance to proc AM on every AB. It's 52% chance with tier. The synergy is going to be fun! This may also help in fixing the flow of mana in the spec
3) Cord of Infinity: After dropping below 40% mana, your mana regeneration is increased by 10% for 15 sec.
Not as great as the others, but actually pretty decent. This helps you during your burst phase, and theoretically you can take yourself to 40% mana during the conserve cycle to provide yourself a bonus in mana regen in time for your burst phase. On its own this may not be that impactful, but it can work well as a second legendary when you have the kilt or armwraps. The simulations may undervalue it because they don't account for intentionally getting to 40% to get the buff.
General:
4) Shard of the Exodar: Your Time Warp does not cause Temporal Displacement on yourself and is not affected by Temporal Displacement or similar effects on yourself.
You can line this up with your second burst phase for a massive DPS boost. Pretty great but situational (is not efficient if you save lust for the end of a fight).
5) Prydaz, Xavaric's Magnum Opus: After not taking damage for 5 sec, you gain an absorb shield for 15% of your maximum health for 30 sec. This effect may occur once every 30 sec.
Has no direct DPS boost, but it can be quite useful in progression. Unless you are taking sustained damage throughout the fight, this can help lower the amount of healing you need. Also can help a bit while solo'ing. I'm not sure if the "taking damage" bit applies through barrier. It may be powerful if that is the case. Perhaps someone on Beta can test this.
6) Belo'virs Final Stand: After casting Blink, you gain an absorb shield equal to 20% of your maximum health for 15 sec.
Better than the previous legendary as it is not contingent on taking damage and shields for more. The same logic applies. However you must blink to gain the effect, and considering that Arcane requires smart usage of shimmer to cast during high movement phases, it's less convenient to use. However high movement phases can coincide with high damage mechanics, making this more convenient for mitigating burst rather than sustained damage
7) Sephuz's Secret: Successfully applying a loss of control effect to an enemy grants you 70% increased movement speed and 15% Haste for 10 sec. This effect may occur once every 30 sec.
Some say this applies on ATTEMPTED cc rather than successful. I'm not sure. Either way, it does not proc on slows and such such as Slow, only with hard CC like Frost Nova.
This may look beyond useless, but it has some use. It actually helps you solo as a mage, and can be pretty effective for mythic+ farming as you can use Frost Nova while in melee against dungeon mobs (or any CC for that matter) for 15% haste. That translates to 15% faster casting of Arcane Explosion into Barrage which may effectively boost your burst.
8) Norgannon's Foresight: Your instant cast spells have a chance to trigger Foresight, making your next non-instant cast spell castable while moving.
Arguably the worst legendary for Arcane in almost all aspects. We only use instant casts for when we AOE or when we are in conserve on ST. Our AOE rotation has no cast times to it, making it have almost no use unless you want Arcane Missiles on the move for some reason to give your mana some reprieve. It may have SOME usage if we want to move after casting an Arcane Barrage during our conserve, but delaying your casting in the conserve cycle won't gimp your DPS that much to make this worth using. It's not even guaranteed to proc.
Honestly this one is so bad it has to be remade for Arcane. There's almost no justifiable use for it.
---
What do you guys think?