Well, I never played Rome 1 online, apart from the EB mod, where they had very low attacking and defensive stats, but were still extremely tough to kill off from the front. I'd only have about 25% of my force be phalanx units and I'd use them in an offensive manner. I'm not sure whether I was abusing an OP unit, they died fairly quickly to mass ranged or flanking, but I know I find it very handy to have stable lines in any battle on which you can pin down the enemy army while you maneuver your other units.
Actually I thought that the phalanx from the video appeared to be very fast moving, and quite resilient to side attacks. I don't doubt that they will be much less buggy and much less prone to derping their formation as they were in Rome, so I think my favourite way of fighting will continue to be viable. So majestic, walls of pikes.