Not important at all. It only affects your saber strikes, Trash and Lacerate.

You do need the cost reduction for Shock. Not so much for Trash. You can drop Trashing Blades if you are still taking it as Trash is out of the rotation.

Dismiss him then Summon him again. Full HP in 1.5sec. In fights, there are medpacks which heals both yourself and your companion.

Don't see how that has got to do with Assassins though..

You are sorely lacking in Defense. Go for Defense.

Surging Charge is only limited to the Deception tree. Both Lightning and Dark Charge are shared between all trees. And no, your alignment does not affect what abilities you obtain.

Do you mean Pureblood specific dialogue options? If you do, then no. There are no species specific dialogue options.

I played Pureblood so I can smack my companions around.

The faster you get Harness Darkness stacks, the more self healing you receive and your Force Lightning does more damage as well. Using Trash to fish for procs is too RNG based while consistently keeping Wither and Shock on cooldown to get Harness Darkness stacks would in longer fights be better. You can read more about our abilities priority on MMO Mechanics. http://mmo-mechanics.com/swtor/forums/Thread-Sith-Assassin-Jedi-Shadow-Tanking-Compendium#Id

No. It is the Sith Inquisitor story. Not the Sith Sorcerer or Sith Assassin story.

It would help if you link your build idea. No one can comment without first taking a look at your build. That being said, the likelihood of it being useful is pretty slim. The trees are now designed in a way that being a hybrid is a pretty poor life choice.

That's not true. With Wither granting Harness Darkness, it is more effective to NOT use Trash to proc Energize. Using Wither and plain casting Shock is now much more efficient.

Only 1 person needs the crystal but everyone needs the MGGS. And yes, you have to be level 50 to use the datacron. You can enlist the help of non-50 players but they won't be able to use it.

Your stats don't really determine what you can tank. It really depends on your group composition and your own skills as well.

That's because you bumped a dead thread that was before there was changes to Raze...