I completely agree with you (as I wrote it here https://forums.totalwar.org/vb/showthread.php?t=97455), espiecially in the light that it takes a hell lot of effort to get those troops (VG, and catapracts). The problem is, in a sense, that vards are very good, and it is very easy to beat up the AI with HA armies. This might be good for the player but it hides the other weaknesses.
So practically early on byz is nothing more than a HA factions with mediocre infantry and some decent archers. IMO more like the turks rather than what it was in historcal terms.
BTW, VG is significant improvement over BI and dism lancers (esp. in terms of moral) but there are better infs in the game (JHI, DCK).