Seriously, the Energy Sword (or Prophets Bane also) is the only Covenant weapon currently in the Beta. Where the heck are they?
they are hidden
Most covenant weapons are analogues of UNSC equivalents, like BR/Carbine, SR/AR. This means they don’t need balancing as badly. As soon as the developer knows that a particular damage and ROF works for another equivalent weapon, they more or less know how to make the covenant weapon function. It might need some very slight tweaks, but nothing major. Thus, there aren’t any covenant equivalents, since they would take up unnecessary space in the beta’s 11 weapons.