Murlocs aren't really the thing they used to be, but they're still a serious nuisance when they show up. The problem with Murlocs is that they're better the fewer Murloc decks there are around, since most of the downside of playing them is that they buff ALL Murlocs, even your opponent's.
Murloc Warleader is a 3/3 for 3, which isn't great, but it's perfectly respectable. The problem is that his +2/+1 buff for other Murlocs puts them into seriously dangerous territory. Even if you just play one per turn -something that's hugely unlikely, given the nature of Murlocs - he'll be adding a total of seven power to the board when he lands on turn three. That's HUGE.
Given that the other tribal deck, Pirates, offers only a +1/+1 buff, and there are fewer of them to begin with, the Murloc lord should definitely be brought in line with its scurvy-suffering counterpart. Don't get me wrong, I love Murlocs. But fair is fair.
4) Savage Roar
I wasn't entirely sold on this inclusion until I started doing the math. The Mage's Pyroblast at 10 mana is already almost too much. Savage Roar, however, when you toss it into a swarm deck, which floods the board with little creatures, is offering significantly more efficiency. For three mana, you can turn a bunch of harmless 1/1 dorks into a veritable death squad.
When you combine it with Force of Nature, you're looking at a devastating 14 damage (including two from your hero) for only nine mana. That makes it difficult to stay in the "safe zone" for health total when you're facing down a Druid. That's not even to mention the corner case where Innervate is in hand. That allows a double Savage Roar, kicking the face-smashing damage total to 22!