>>527626995
see pic related written by Halsey herself. most covenant technology was fucking magic and the only reason the UNSC managed to get shields working was because the energy gauntlet they stole from a kigger was a out of date chinese knock-off.
>>527628669
covenant weapons are obviously designed to fight sentinels since the covenant probably pissed them off on multiple occasions and plasma weapons are shown to be highly effective against them both in game and in lore.