Druid

Two main characteristics of Druid deck are

1 Mana Manipulator

We always constraint by the mana given each term. Every Hero need to follow the mana curve except Druid. Druid owns three extraordinary spell cards which allow him to manipulate the mana curve.

Innervate gives you instantly 2 extra mana in the turn that you play it. If you play it earlier, you gain a stronger board control. If you play it latter, you can play combo where it is impossible for others due to limitation of 10mana. The tradeoff is you lose a card. So make sure you have some card drawing effects in a Druid Deck.

Wild Growth extorts your mana curve by increase you total mana by one after playing it. If you manage to play it on turn 2, the total extra mana you gain are equal to -2+1+1+1+1+1+1+1+1=6. If you draw it after turn 10, don’t worry, it can be exchange for a card draw. Although use 2 mana to draw a card is not worth (usually 1.5) 

2 King of Choice

Most of the Druid specific cards (whether minion or spell) have two effects to choose from. It give you more choices and make a suitable choice in most of the situation. So you can play those cards easily on the same times do not wasting the effect of the cards. 

Let us see the overall stat of Druid specific cards.

1 Card Drawing Effect

2 Area Damaging Spell

3 Buffing

4 Defensive Play

Druid has the most minions and buff that give taunt effect.

5 Offensive Play

Druid has quite a lot cards that give direct damage to opponent life.