Well there ya go, I just learned something

. Another thing to note, you need scarabs in your ret phalanx. And you want a couple more than 3 bases so they can survive a bit longer before they go down.
Automatically Appended Next Post: Well if that's the case you could load up your overlord if you don't want to buy more models. Warscythe, phase shifter and a veil of darkness makes him much more survivable and choppy. I would add a gloom prism if your going to be up against eldar, it would work pretty well in low points games such as this.
So if you didn't want to buy too many more models you could run something like this:
Retribution phalanx -
1x overlord w/ warscythe, VoD, phase shifter
1x stalker with Heat Ray
20x Warriors
6x scarab bases
Canoptek harvest -
1x spyder w/
TL PB, gloom prism
4x wraiths w/ coils
5x scarab bases
You'll probably find you won't use the phalanx rule as much with the higher squad numbers.
Hope this helps, have fun!