I don't play a Vanguard, but I do have a Powertech Tank, and I've been researching a lot. If you don't mind doing a lot of reading, you should read this post on Powertech/Vanguard tanking: http://sithwarrior.com/forums/Thread-The-Shield-Tech-Shield-Spec-Compendium
If you want to really get into damage mitigation research, and you're good with math and Excel spreadsheets, check out this post: http://sithwarrior.com/forums/Thread-Tanking-stat-spreadsheet-online
I also have a slightly different view than Lazerender for your skill tree: http://www.torhead.com/skill-calc#801G0GrdorogzZMsbZb.1. I suggest removing the 2 points in Brutal Impact, as High Impact Bolt has such a long CD (15 seconds). Instead, I'd recommend putting the extra point in Shield Cylinder and Smoke Grenade. The reason for this is that the passive 1% shield increase paired with the extra 25% chance to generate an energy cell is quite useful. The Smoke Grenade acts as another defensive CD during heavy attacks, because it reduces the accuracy of all enemy targets within range by 20%. This is imperative for Ops/Raids, because we don't get much in the way of defensive cool downs. As for the extra 2 points unnassigned by Lazerender, I personally like to put these points into Power Armor for the 2% damage reduction.
I am by no means an expert, but if you have any other questions, let me know and I'll help you research further!