i think when some1 grabs a shield they wanna tank correct? so why dont we buff its threat generation? i know theres a “threat” mechanics because bosses wlil attack whomever is hurting them the most.
when shielded weapon crits, or when you do a block push (shield bash, not the shield charged attack), all enemy hit are forced to strike you once. this effect stacks. so if you wish to tank and hold aggro, run into a mob and shove and bully the horde around and they all forced to attack you for however many times you’ve bashed them.
just to give shield a purpose 
oh and i’m not sure if this OP enough to work on bosses or not L_L
edit: oh and this force attack debuff on enemies probably shouldn’t last forever now that i think about it. how about a 5 or 6 seconds duration lol