Oh trust me, its not just the zap from my experience.
Look at those numbers. Notice how just wearing a helmit and light armor (a total of around 200 credits.. oh my!) makes it so humans instantly take 3x-4x less damage for such a cheap price. This SERIOUSLY hinders aliens that either are not an experienced goon player that know when to run away and strike at the right time, or a maradur player who can easily hold his own against human fire due to dodgeing.
Honestly, a lone dretch against a lone human at S1 will be a fairly even match. The human has range and letal accuracy, while the dretch has high manuverability and a letal bite.
Once you get to S2 however, things change. The human with Helmit and Armor plus a pulse rifle against say an adv. baslisk or an adv. maradur, and the human easily has the upper hand, seeing as only 24 or so damage max is done to a guy with a helmit is done, and thats IF you can get close. And for how much? 200 credits (or so). That is not alot at all, considering the benefits (RADAR, poison gas doesnt do anything, ect).
I'm not saying make the 2 sides exactly the same. I am saying that human's technology is way to cheap for what its worth once they get to S2. There is a reason in many RPG games armor tends to cost alot more than say a good sword, because it helps alot in defense. The same is for tremulous, execpt that the armor is dirt cheap.