Reason why Aliens have such a strong early/ Mid game
The reason why aliens are dominating the early to mid game is due to the fact that they do not need to build anything. The alien commander just drops it and it builds itself. Leap being researched right away is not the cause of the alien dominance early game. In small games such as 3 v 3 the marines are require a commander then need 1 to defend and 1 to build, while the aliens require a commander and the other 2 players can just roam map and take out the marines resources or harass the marine base. This drastically slows down marine progression in the early to mid game. Even in larger games this is very noticeable. The alien commander can cap all the resource nodes while the rest of the alien team goes on the offensive. In NS 1 there was a trade off if you sent all of the aliens in for a base rush and the marines were able to hold you off it cost you resources since you didn't have anyone capping resource nods. Now there is zero trade off for aliens having all but one alien zerg the marine base. They do not lose any time capping resource nods which allows them to further evolve with no consequence.