Phalanx's are awful mainly for one reason. When the A.I. advances towards your line all phalanx's, at the last moment will turn about 45 degrees and attempt to attack the flank of the unit next to yours. This is basic shitty A.I. coding that is hardcoded. No matter what nice formations you set up for the phalanx, you can never get around this issue.

One on One, phalanx's behave fine, however once a second unit is next to one of yours, the A.I. uses the phalanx incorrectly.

Believe me if the A.I.'s phalanxs attacked head on, then Darth's Phalanx formations would be extremely good.