The question I have for you, and all Tanks in general. Grabbing aggro when you're in a HM or OP which requires CCing some of the tougher elements of the fight. In that situation you can't use AOE taunts or Mortar Volley without breaking CC.
What's the best rotation to use in that situation? I rely heavily on single target taunts, and storm. It's a heckuva lot of work that way but hey, that's our job...
You are right, there is more work involved when you have to deal with groups in HMs and Ops. Best rule of thumb is keep as many of them on you as possible, but the harder the targets, the more the priority. If you don't have aggro on every single normal, who cares, they die fast. But if an elite is attacking your healer, that obviously becomes a problem. I save my Neural Jolt in fights like that so that it's available if i need to get an NPC off a group memeber.
When you have to deal with CC'd targets, it really depends on what the NPC composition is like. For example, in False Emperor Hard Mode, there is a group right at the first corridor that consists of 2 Elite droids, 2 Strong Sith(melee), and 3-4 normals. What i will generally do in that situation is pull aggro by attacking or taunting one of the Sith while 2 of my group members CC the big droids. I'll make sure i have aggro on the 2 Sith, and then just have the group take out the normals first, then the strongs, and then we go to the droids. CC-ing makes all the difference in the world on the harder stuff. In other scenarios, you won't CC anything, and then you just taunt the heck out of the group, and have your dps just start picking off targets.
I only use Mortar Volley if there is nothing to CC, or i find a way to get the CC'd target(s) away from the rest of the group so that we can all use our AoE abilities. I tend to swap targets a lot during a fight to make sure i keep damage going out to all targets. They really improved stuff with 1.3, with the addition of the Ion Cell threat boost from 50% to 100%, and little ability boost, such as the fact that High Impact Bolt now works with Ion Cell in a close range AoE.