Your shouts might be on cooldown, but your charge shouldn't. So charging in, hitting thunderclap and get those mobs together for your shockwave. Rend, thunderclap again and don't forget about cleave.
You could also specc into the Blitz talent for additional 10 rage with every charge and don't forget about to mark at least one mob with a skull/desired raid symbol for your dps to nuke.
Regarding the warlock: "You pull it, you tank it." If they won't stop after being asked nicely let them learn the hard way and if they still proceed being unconvincable there's always a 'vote: kick player' option.
Gemming advice: Cata content is not here yet so getting as much stamina as possible is still advisable, ignoring all socket bonus despite one (preferable helmet) to meet your meta requirements.
Shield: 18 Stamina
Weapon: Blood Draining
And i'd highly recommend spending those 70 honor points and grab yourself a Wrathful Gladiator's Shield Wall. Despite still saying it has a rating requirements all below 2000 have been lifted with the 4.0.x patch.