IMO armories are generally worth less than they cost. I'd rather put that 75 res towards research or tanks and tell my team to rely on engies for ammo and health. I'm all for getting rid of the things and putting ammo and health boxes in barracks.
in the previous version armories had more hit points than any other building i believe. they changed for the better IMO.
Everything had the same HP, they've revamped and raxes and VFs have the mos thealth, while refs armories radars and repair stations have less hp.