Blizzard, like many other MOBA developers, periodically “reworks” older Heroes of the Storm characters so that they’re relevant in the meta. This can happen if a hero falls out of favor due to eventual power creep, or because their kit just isn’t plain fun — for Tyrael, it’s a lot of the former.
The high mana-cost warrior has had low pickrates for some time, and although it’s far past due the Archangel of Justice is back. Among general buffs like mana reduction he seems a lot more proficient at solo laning, which already makes him more interesting. The changes seem sound, but the fact that his boring kamikaze passive — which doesn’t feel on-theme at all — wasn’t altered is disappointing.
Alongside of the rework comes a new skin for the hero, Mecha Tyrael. Tyrael now joins Mecha Tassadar and several others (including the new Mecha Rehgar skin) to form a Voltron of anime skins.
Heroes of the Storm Patch Notes [Battle.net]