The riot shield is fantastic in HC. Just gotta use it right. I made some dude suicide off the edge of Carrier
Yeah, you'll get killed a lot if you go shield only, but when you get someone where you want them its soooooo funny to use hahahaha!
I had no problems leveling up and getting my Riot Shield gold during the double weapon XP weekend a few days ago. Just use Fast Hands and concussion grenades to stun people and then bash them to death. It's pretty easy.
I think the biggest issue with the shield is basically getting shot through it when someone sees you and starts shooting lol if the shield cruelly blocked bullets consistently it would be far easier since the melee delay is short in this game