Reintroduce Classic Mode with these changes.
Here is the few changes I propose to bringing back Classic Mode (instead of Casual Mode):
Reduce problematic exploitative draw and/or damage cards.
1a. Northshire Cleric | Whenever a minion in damaged, it restores 1 Health.
1b. Starving Buzzard | Whenever you summon a Beast, gain 1 Mana Crystal this turn only.
1c. Cult Master | Whenever a friendly minion dies, gain 1 Mana Crystal this turn only.
1d. Gadgetzan Auctioneer | Whenever you cast a spell, gain 1 Mana Crystal this turn only.
1e. Jaraxxus (because of The Coin and Harrison Jones) | [10 Mana] 4/4 Bloodfury.
1f. Archmage Antonidas (because of The Coin) | Whenever you cast a Class spell, add a ‘Fireball’ spell to your hand.
1g. Velen | Battlecry: Draw a damage spell and upgrade your starting Hero Power.
1h. Edwin Vancleef | 3 Attack, 3 Health. Combo: Gain +1/+1 for each card played earlier this turn.
Reduce the assortment of semi-problematic exploitative draw and/or damage cards.
2a. Flare | All minions lose Stealth. Destroy an enemy Secret. Draw a card.
2b. Eaglehorn Bow | Whenever a Secret is revealed, gain +1 Attack.
2c. Scavenging Hyena | 2 Attack, 3 Health. Whenever a friendly Beast dies, gain +1/+1.
2d. Wild Growth (with no 0-Cost spell)| Choose One - Gain an empty Mana Crystal; or Gain 4 Mana Crystals this turn only.
2e. Nourish | Gain 2 empty Mana Crystals; or Draw 3 cards.
2f. Mana Wyrm (because The Coin) | Whenever you cast a class spell, gain +1 Attack.
2g. Ice Lance (because of Alexstrasza) | Freeze a character. If it was already Frozen, deal 3 damage instead.
2h. Equality (because of Wild Pyromancer) | Silence a minion and change its Health to 1.
2i. Divine Favor | Draw cards until you have 4 cards in hand.
2j. Sword of Justice | [4 Mana] 3 Attack, 3 Durability. After you summon a minion, give it +2/+2 and this loses 1 Durability.
2k. Holy Wrath (because of Molten Giant) | Draw a card and deal damage equal to your highest Cost card in hand, up to 10.
2l. Tirion Fordring | 7 Attack, 7 Health. Divine Shield, Taunt, Deathrattle: Equip a 4/2 Ashbringer.
2m. Inner Fire (because of Divine Spirit) | Change a minion’s Attack to be equal to its Health, up to 10.
2n. Auchenai Soulpriest (because of Circle of Healing) | Battlecry: Your next Hero Power deals damage instead.
2o. Cold Blood | Give a minion +2 Attack. Combo: +3 Attack instead.
2p. Blade Fury (because of Deadly Poison) | Destroy your weapon and deal its damage to all enemies, up to 3.
2q. Windfury (because of Leeroy Jenkins) | [4 Mana] Give a minion Windfury and +5 Health.
2r. Flametongue Totem | [3 Mana] Friendly non-Totem characters have +2 Attack.
2s. Power Overwhelming | [2 Mana] Give a friendly minion +4/+4 until it takes damage. Then, it dies. Horribly.
2t. Grommash Hellscream | [7 Mana] Charge, Enrage: +4 Attack.
2u. Hungry Crab | 1 Attack, 3 Health. Whenever the opponent summons a Murloc, gain +1 Attack.
2v. Lorewalker Cho | 0 Attack, 5 Health. Taunt. Whenever a player casts a spell, Cho becomes enlightened (gains Divine Shield).
2w. Raging Worgen (because of Charge) | Enrage: Rush and +1 Attack
2x. Twilight Drake (because of Warock’s Life Tap) | 4 Attack, 3 Health. Battlecry: Gain +1 Health for each other card in your hand.
2y. Doomhammer (because of Harrison Jones) | 3 Attack, 5 Durability. Windfury, Overload: (2)
Give to the 3 slightly lacking Classes.
3a. Paladin gets a good all-around removal option (Equality).
Equality (because of Wild Pyromancer) | Silence a minion and change its Health to 1.
3b. Hunter gets good all-around removal option (Deadly Shot).
Deadly Shot | [4 Mana] Destroy the enemy minion with the highest combined (current) Attack and Health.
3c. Priest gets a good all-around removal option (Mind Control).
Mind Control | [7 Mana] Take control of an enemy minion. If it didn’t Attack, Silence it first.
Fix the 1 stupid card.
Deathwing | Battlecry: Destroy a minion. Deathrattle: Discard 2 cards.
Force of Nature | Summon three 2/2 Treants, one with Charge, one with Rush, and one with Taunt.
Battle Rage| Draw a card for each damaged friendly character, up to 2.
Counterspell | Secret: When your opponent casts a Class spell, Counter it.
Silverback Patriarch | [2 Mana]
Booty Bay Bodyguard | 4 Attack, 5 Health.
Lord of The Arena | 5 Attack, 6 Health.
Priestess of Elune | [5 Mana]
Ravenholdt Assassin | 6 Attack, 6 Health.
Core Rager | 8 Attack, 6 Health.
Frost Elemental | 6 Attack, 5 Health.
Stormpike Commando | 4 Attack, 4 Health.
Nightblade | Stealth. Battlecry: Deal 3 damage to the opponent’s hero.
Mogu’Shan Warden | 2 Attack, 6 Health.
Tauren Warrior | 2 Attack, 4 Health. Taunt, Enrage: +1 Attack.
Raid Leader | 2 Attack, 3 Health.
Magma Rager | 6 Attack, 1 Health.
Ironforge Rifleman | 2 Attack, 3 Health.
Dalaran Mage | 1 Attack, 5 Health.
Alarm-o-bot | 0 Attack, 4 Health.
River Crocolisk | 2 Attack, 4 Health.
Pint-Sized Summoner | 2 Attack, 3 Health.
Blood Knight | Battlecry: All minions lose Divine Shield. Gain +1/+1 for each Shield lost.
Murloc Tidehunter | Summon two 1/1 Murloc Scouts.
Frostwolf Grunt | 2 Attack, 3 Health.
Bloodfen Raptor | 4 Attack, 2 Health.
Murloc Raider | 2 Attack, 2 Health.
Goldshire Footman | 2 Attack, 2 Health.
Elven Archer | 2 Attack, 1 Health.
Angry Chicken | 0 Attack, 3 Health.
Wisp | 0 Attack, 2 Health. Charge.
Captain’s Parrot | 2 Attack, 1 Health.
Mortal Strike | Deal 5 damage. If you have 12 or less Health, deal 6 instead.
Heroic Strike | Give your hero +4 Attack this turn. Gain 2 Armor.
Cruel Taskmaster | 2 Attack, 3 Health.
Summoning Portal | 0 Attack, 5 Health.
Pit Lord | 5 Attack, 7 Health.
Void Terror | 3 Attack, 4 Health.
Shadow Bolt | Deal 4 damage.
Drain Life | Deal 2 damage. Restore 3 Health to your hero.
Felguard | 3 Attack, 6 Health.
Felstalker | Rush, Battlecry: Discard a random card.
Flame Imp | Battlecry: Deal 2 damage to your hero.
Blood Imp | 1 Attack, 2 Health. Battlecry: Give a friendly minion +1 Health.
Sacrificial Pact | [1 Mana] If you control a friendly demon, restore 5 Health to your hero.
Lava Burst | Deal 5 damage. Overload: (1)
Far Sight | Discover a card from your decl. That card costs (3) less.
Stormforged Axe | [1 Mana]
Forked Lightning | Deal 2 damage to 2 random enemy minions. Overload: (1)
Dust Devil | Windfury. Overload: (1)
Wrath of Air Totem | 0 Attack, 1 Health.
Kidnapper | [5 Mana]
Perdition’s Blade | Battlecry: Deal 2 damage. Combo: Deal 3 instead.
Headcrack | Deal 4 damage to the enemy hero. Combo: Place this on top of your deck.
Patient Assassin | 1 Attack, 2 Health.
Holy Fire | [5 Mana]
Mind Games | [5 Mana] Discover a copy of a minion from your opponent’s deck into the battlefield.
Lightspawn | [3 Mana] 0 Attack, 4 Health.
Shadowform | [2 Mana]
Mind Vision | Discover a copy of a card in your opponent’s hand into your hand.
Truesilver Champion | Whenever your hero attacks, restore 3 Health to them.
Argent Protector | 2 Attack, 3 Health.
Repentance | Secret: After your opponent plays a minion, actually reduce its Health to 1 (so if it has 1 Health, this doesn’t trigger).
Pyroblast | [8 Mana] Deal 9 damage.
Spellbender | Secret: When an enemy casts a spell on a minion, summon a 2/3 as the new target.
King KRUSH | [8 Mana] Rush.
Gladiator’s Longbow | [6 Mana]
Misdirection | Secret: When an enemy attacks your hero, instead it attacks an actual other random character (so it doesn’t attack the same character).
Tracking | Discover a card from your deck.
Mark of Nature | [2 Mana]
Naturalize | [3 Mana] Destroy a minion. Your opponent draws a card.
Moonfire | [1 Mana] Deal 2 damage.
Edit: Lightwarden | Whenever a character is healed, gain +1 Attack.
Secretkeeper | Stealth. Whenever a Secret is played, gain +1 Attack.