Arthas (Rework) by MrCobweb

Blood Presence
Basic Attacks and Basic Abilities heal you for 15% of the damage dealt.

Frost Presence
Basic Attacks increase your Ability Power by 10% for 5 seconds.

Unholy Presence
Basic Attacks and Basic Abilities poison enemies, dealing an additional 10% of the damage dealt as poison over 2 seconds.

Uncoil (Q)
Death Coil explodes for area damage, dealing 50% damage to surrounding enemies.

Obliterate (W)
Every third consecutive Basic Attack against the same target reduces the Mana cost and radius of your next Howling Blast by 25%.

Plague Strike (D)
Damage boost of Frostmourne Hungers increased to 200%, but is dealt as poison damage over 4 seconds. Lowers the cooldown of Frostmourne hungers by 2 seconds.

In Debt with Death
Passively grants 5% Maximum Health. Every time Arthas dies he gains 5% more Maximum Health, to a maximum of 25% extra.

Plaguebearer (Q)
Death Coil and Howling Blast poisons enemies hit dealing 50 additional damage over 3 seconds.

Frozen Wastes (E)
Every 2 seconds Frozen Tempest is active increases its radius by 20%, up to 100%.

Frost Strike (D)
Frostmourne Hungers also slows the target by 40% for 1.5 seconds. Lowers the cooldown of Frostmourne Hungers by 2 seconds.

Conversion
Cooldown: 30 seconds
Activate to heal 30% of your max Health over 8 seconds. You do not regenerate Mana during that time.

Rune Tap
Using Death Coil or Howling Blast while the other is on cooldown reduces damage taken by 40% for 3 seconds.

Freezing Rage (E)
Every second Frozen Tempest is active increases its damage by .3.

A Legacy Lost
While Frostmourne Hungers is on cooldown your Basic Attack damage is increased by 50%, but all regeneration effects and healing received is reduced by 50%.

Tenacious DK
Nearby slowed and poisoned enemies reduce the duration of silences, stuns, slows, and roots against your Hero by 33% per enemy effected.

Immortal Coil (Q)
If Death Coil kills an enemy its cooldown is reset and the damage of your next Death Coil is increased by 20%.

Mind Freeze (W)
Enemies hit by Howling Blast become Hindered, causing their abilities to recharge 50% slower for 10 seconds.

Death Strike (D)
Frostmourne Hungers deals 20% more damage for each 10% of life the target is missing. Heal for 5% of your Maximum Health.

Legion of Northrend (R)
Sacrificing a Ghoul increases the duration of remaining Ghouls by 2 second. Increases the number of Ghouls by 3.

Absolute Zero (R)
Sindragosa flies twice as far. Enemy heroes are rooted for 2 seconds, and then slowed by 60% for 2 seconds.

Frostmourne Feeds (D)
Hero Takedowns refreshes the cooldown of Frostmourne Hungers.

Master of Ruin
Increase the damage and duration of slow and poison effects on nearby enemies by 1 second every second.

Arthas has always been one of my favorite characters in fiction. To add to that, Death Knights have long held a special place in my heart. I chose to do this rework not because I believe the developers did a poor job with the character but rather because I feel they didn't do enough. Playing Arthas in HotS never quite felt like I was controlling a true Master of the Wastes. I will briefly discuss the subtle changes, talents, builds, and playstyles I envision for Arthas.

Changes to abilities:
All-in-all his abilities were on point. Death Coil and Howling Blast both fill roles needed for the character. Frozen Tempest does its aoe thing . I also swapped Frostmourne Hungers mana gain to 5% of max Mana to keep his mana pool decent as the game progresses.

Changes to Specs:
Arthas is currently designed to mostly fill the tank role. I always envisioned Death Knights as fully rounded characters capable of filling multiple roles. Because of this I approached the character similar to Kharazim, in that you pick your specialization from the very beginning. If the team needs a tank, you can go Blood Presence. If the team is light on dps, pickup Frost Presence for some boosted damage. If the team has no efficient laners, grab Unholy Presence to clean up lanes quicker. Versatility for different team comps/maps lends itself nicely to the capabilities of a Death Knight.

Changes to Playstyle:
Death Knights play more like combo characters than anything else. I opted to make Arthas' talent tree reflect this philosophy. Paring Unholy Presence with Uncoil lets you self-heal with Death Coil but also poison enemies near you. Tanks can grab Rune Tap for improved initiates