Adjustments to the weight of Rogue class cards have been made. Also, last week, the current rules for Arena were posted after the release of Rise of Shadows.
It looks like Rogue may have been a tad too powerful in Arena, after the release of Rise of Shadows. Team 5 is adjusting the weight of Rogue class cards, with overperforming ones being seen less frequently.
Later today we will be applying an adjustment to the weight of Rogue class cards in Arenas to address some current balance issues. This means that overperforming Rogue cards will be seen less frequently. Additionally, we will be making changes to the card buckets for other classes to create a more consistent drafting experience. You will not need to patch your client or download any additional data to receive this update.
Please note that after this change some Rogue choices may seem sub-optimal, but we are prepared to address any outstanding issues in a future update. (source)
Rise of Shadows brought a significant change to the Arena, as it now has a rotating draft pool. Accordingly, Blizzard has posted an update to the current Arena rules:
Update 14.0 – 04/09/19
Any given Arena draft pick will offer 3 cards from the same “Bucket”. There are currently 13 non-Legendary card buckets and 5 Legendary card buckets.
On average, Arena draft picks consist of about 79% Common, 15% Rare, 5% Epic, and 1% Legendary cards.
Your 1st, 10th, 20th, and 30th picks will be guaranteed to offer cards from Bucket 4 or higher.
Class cards receive an additional +50% increase in their appearance rate.
Spell and weapon cards OR cards from the latest Expansion receive an additional +50% increase in their appearance rate.
Neutral cards from the Classic and Basic set appear 50% less often.
These appearance rate modifiers are multiplicative.
The following cards are unavailable to be drafted in Arena:
Ancient Watcher, Mind Control Tech, Klaxxi Amber-Weaver, Dark Arakkoa, Cult Sorcerer, Twilight Darkmender, Hooded Acolyte, Blade of C’Thun, Usher of Souls, Ancient Shieldbearer, Twin Emperor Vek’lor, Disciple of C’Thun, Doomcaller, C’Thun, Beckoner of Evil, C’Thun’s Chosen, Twilight Geomancer, Twilight Elder, Crazed Worshipper, Skeram Cultist, Jungle Giants, Open the Waygate, The Caverns Below, Vicious Fledgling, The Marsh Queen, Fire Plume’s Heart, Awaken the Makers, Unite the Murlocs, Lakkari Sacrifice, The Last Kaleidosaur, Humongous Razorleaf, Bloodreaver Gul’dan, Deathstalker Rexxar, Frost Lich Jaina, Malfurion the Pestilent, Scourgelord Garrosh, Shadowreaper Anduin, Thrall, Deathseer, Uther of the Ebon Blade, Valeera the Hollow, Baku the Mooneater, Black Cat, Genn Greymane, Glitter Moth, Gloom Stag, Hagatha the Witch, Murkspark Eel, Dr. Boom, Mad Genius, Whizbang the Wonderful, Zul’jin, Arcane Watcher
Arena Bucket Information can be found here 32.
We’re always working to improve the Arena experience, and your feedback is appreciated!