One of the main problems at the moment with finishing an alien victory is actually forcing entry into the marine spawn and destroying important structures. There's a number of issues combining here:
At this point, the entire marine team is concentrated in one place. That means your assault is charging into the muzzles of the entire team's LMGs, and that adds up. The situation gets worse if they have bigger guns, or one of those spawn areas that has good lines of fire, and is one of the reasons that the lighter lifeforms that would theoretically be ideal for this kind of fight (Lerk for crowds of marines, Gorge for crowds of buildings) have a hard time staying alive for any length of time.
There's no real loss for marines who buy a shotgun, GL, or flamethrower and then die three seconds later, because one of your teammates can just pick it right back up again. Hell, YOU can pick it right back up again, since you'll be alive and on location again in 10 seconds. That means that those "bigger guns" I was just talking about don't actually get removed from play when their owner dies, unlike an Onos or Fade who gets chopped up during the assault; as long as there's an Armory intact in the area, those big guns effectively never come off the line.
The marines have no travel time after respawning to delay reinforcing their frontline (which is five feet away from the IP), whereas alien reinforcements are coming from all over the level. "Keeping pressure on them" is very difficult when you have an equal number of players on either side, but one side has a lot of distance to cover; the presense of "extra bodies" in the form of MACs repairing base structures and sentry guns firing at incoming aliens does not help this disparity at all. If the marine team has managed to get an ARC or two dug into their base, you've got even bigger problems, as alien forward operating bases can't be safely set up.
Upgrades for aliens take time, upgrades for marines are instantaneous. Gestating into your preferred assault lifeform takes a while, again making it difficult to maintain pressure after an assault, whereas the marines simply need to pick up the weapons they dropped when they died a few seconds ago, or spend a couple of seconds accessing the armory. The premier breaching lifeform, the onos, has a 35 second gestation time... add in travel time from a hive, and the death of an onos takes about a minute to come back from.
These issues should be addressed (IMO), but in ways that don't necessarily change early-game play. I've got a few ideas, and I'm sure others will have some of their own. I'm also sure some of you don't feel these are issues or will point out that there are different issues in organized play (I'm a pub player, but have clanned in the past, and understand there are significant differences), but the discussion could be handy.
Some ideas to address this:
Rapid transport for Kharaa: likely on the Shift, allow the alien commander to have one of his mature shifts designated as the "receiving point" for other shifts, which are then Used similar to the movement towers of NS1 for teleportation to that location. This would be a 3+ hive ability for the tower, to prevent early game skulk rush insanity.
Allow alien attacks to destroy dropped weapons (either corrosive types like acid spit/bilebomb, or all of them). This will allow the Kharaa to more rapidly sap the PRes pools of marines dug into their last holdout by preventing "hot-potato" shotguns and GLs from moving from one marine to the next quite as much.
Shorten gestation times based on the number of hives. This will allow for more rapid reinforcement of an endgame breaching party, but not change early-midgame play much.
Add 2/3+ hive abilities to the lerk and skulk, who don't really benefit from multiple hives at this time (Leap aside). Xenocide never seemed that useful in NS1, but if it left behind a lingering Umbra cloud, that might be a great way to open an assault. Give lerks something amusing at 3+ hives like acidic clouds... damaging to both people and buildings, or give them rapidfire acid rockets so they can go on strafing runs.
Allow the alien commander to set the default hive people spawn at. While players will still have the option to rightclick and hop to a different egg, the commander could pick which hive is initially selected. This will save a couple of seconds of orientation and changing spawn locations for skilled players, and will put those players who are a little less apt and don't understand things like "you can pick which hive you spawn at" in a good location for the grand strategy.
Create some kind of effect for Croach (infestation) vs. marine structures. If my assault has progressed to the point that I'm en-Croaching upon the marine base, I should really get some benefit from that. Slow damage to structures, slow depletion of the MAX health on a power node (meaning it's more and more fragile until the infestation is cleared, or it fails on it's own), or late-game multi-hive abilities from mature support structures onto enCroached areas (ranged projection of Umbra, improved healing in a given area, projection of the disorientation effect) would allow for more aggressive uses of Croach. While we're at it, allow for Mature Cysts that are more heavily armored and spread lovely alien goo over a larger area, to allow for more aggressive frontline use of Croach.