From first look, your gear checks out fine. I would say you should continue to run heroics and get a Nax 10 group going, if possible.
In my opinion, putting points into improved disciplines is somewhat pointless if you're not going to use the Shield Wall glyph and/or the Last Stand glyph. A 4 minute shield wall is OKAY, but for the content you are currently running, I don't see a need for points to be placed into this talent. A 4 minute shield wall and a 2 minute last stand make sense, and a 2 minute shield wall and a 2 minute last stand make even more sense. You could probably take those two points and put them into Cruetly - just for the added crit/threat. Later down the road when you start doing content that requires the shortened cooldown times, I'd advise having a 2 minute shield wall and a 2 minute last stand.
As for tanking multiple mobs, I find it a lot easier to mark one target skull, make sure the DPS are focusing that target...while you focus on that target, threat wise, and using your thunder clap/shockwave every time it's off cooldown to gain threat/aggro on the other mobs. By the time skull dies, you should have a nice amount of threat on the other mobs so your DPS can AOE them down without the worry of pulling aggro (warlocks using SoC can sometimes pull). This, of course, only works if you're running a group that will listen/follow directions.