Well allow me to start this delayed trend by making a statement:
Druids are Overpowered...
but it is not as apparent as with other classes.
The main reason for this is that other classes dominated usually had one single card that was way more noticeable. Blood Imp always made sure that the warlocks minions survived the AOE. The fiery red color of Pyroblast was always the last thing you would see in a duel.
Druids have no cards like that, rather I would say that the problem is that too many of their cards are individually better than the cards of other classes of equivalent cost. A lot of this also comes with the versatility of the "choose one" mechanic of druids. Now I get that Druids was supposed to be Jacks of all trades afterall. However it seems to me that Blizzard forgot the "master of none" part that is usually followed to balance that kind of design. So here are some of the cards that I would suggest should have a look.
Wraith: This one is easy because there is 2 cards of same value that it can be compared to. The first is demonfire the warlock card. Wraith's first effect deals 3 damage to a minion where as demonfire only deals 2 damage even through both cards have a secondary effect. The second card to compare is shiv, which is exactly the same as Wraith second effect, even through shiv doesn't have any second effect. And no, the fact that shiv can be cast on heroes is actually completely neglectable.
Swipe: The card of comparison here is the paladin consecration the “basic” 4 cost AOE. Now the first alarm sign should be that consecration will only do more damage than Swipe if there are 3 minions or more on the field (assuming no overkill). But the real problem is the damage distribution of Swipe is extremely favorable and very often matches the exact lineup of minions on the opponents field. You are more likely to see some 1 HP minions and 1 high HP than having several 2 HP minions. Its high damage on primary target also allows it to be used as single target which, while not that effective is possible to gain an edge.
Keeper of the groove: Looking at the usual “stat price” of silence, this one is actually on point to an extend. It's stats is actually slightly lower but it is mostly paid in attack, which is better than paying it in health which is typical for silence minions. However that is just for the silence. Looking at it's damage effect through, it is actually ridiculously overpowered. Now take note that this is mostly because other cards that have a “deal damage effect” pay ALOT of stats for that. A comparison would be stormpike commando, which have the reverse stats for same effect even through he doesn't have a secondary effect and cost 1 more.
Conclussion: I can't say that either of these cards are a problemcard, because none of them are that overpowered. The problem is that druids as a whole have too many cards that are just a little over the top. Now as to what I would see changed, it is tough. Wraith doesn't have much that can be adjusted before it becomes a really bad card. Keeper of the Groove is likevise through losing one health could do it. Swipe on the other hand is easy. I would honestly see that Swipe only dealt 3 damage to it's primary target and I think that would be a good change for a start.
So I should probably wrap this up. If you have made it this far then it hopefully means that my post wasn't too whiny. If you have other ideas then leave a suggestion. Just please leave it constructive so this doesn't end up looking like the other classforums whinefests.