Cool to hear another game did that and because I just finished Banner saga and have some free time here are some ideas I have for it.
Warrior-equip a 2/1 axe
Paladin-heal a minion by 3 health
Rouge-give a minion +1 attack
Druid-Give a minion taunt
Hunter-give a minion +1 health
Shaman-Restore 3 health to your hero.
Priest- add a 1 mana draw 1 random card from your opponents deck to your hand
Warlock- lose 2 health deal 2 damage
Mage- equip a 0/2 wand with spell damage +1 when you cast a spell lose 1 durability.
Ok I was struggling on some of those but I tried to come up with reasonable ones.
A while ago I had the idea of making Hero Powers a "Choose One" button to make matches more interesting. I say that because some of these Hero Powers would be terrible if they were your only one, lol. Here's the list:
Rogue:
Equip a 1/1 weapon.
Give your weapon +1 attack.
Your character does not take damage when attacking this turn.
Warrior:
Gain 2 armor.
Give a minion +1 health.
The next minion you attack with a weapon takes an additional 2 damage.
Hunter:
Deal 2 damage to the enemy hero.
Give a minion +1 attack.
Summon a 1/1 Beast.
Mage:
Deal 1 damage to a character.
Gain +2 spell damage until your next turn.
Freeze the next single character that you deal damage to this turn.
Priest:
Heal a character for 2.
Look at the top card of your deck. You may shuffle it to the bottom of your deck.
Deal 1 damage to a minion at the start of the next 3 turns.
Paladin:
Summon a 1/1 Soldier.
Reduce a minion's attack by 1 this turn.
The next minion that attacks you takes 2 damage.
Shaman:
Healing Totem (0/2 heals all friendly characters for 1; yes, a small buff)
Stoneclaw Totem (0/2 taunt)
Wrath of Air Totem (0/2 +1 spell damage)
Remake Searing Totem into a 0/2 for 1 that cannot attack and deals 1 damage to a random enemy character at the end of your turn. This is more in-line with its WoW parallel.
Druid:
Gain 1 armor, and 1 attack this turn.
Heal a minion for 1 at the start of the next 3 turns.
Next turn only, gain 1 mana crystal.
Warlock:
Draw a card and take 2 damage.
Deal 2 damage to a friendly minion, and heal 2 life.
The next minion you play from your hand this turn gains +1 attack and health.
