Nice guide Zab, well put together. I liked the section comparing shadow tanks to guardian tanks. The only thing I would comment on is
Slow Time. This skill is so amazing, that this alone is what makes this spec a close second to 22/17/2. Slowing up to 5 enemies by 30% and reducing their damage done by 5% per person that it hits. So if it hits the maximum of 5 dps they will be doing 25% less damage altogether to the people they are attacking. Also each time you use Slow Time you get a Harnessed Shadows proc.
They are still only doing 5% less damage. If 5 players each deal 100 damage (total 500) before slow time. After slow time they are each doing 95 damage (475 total). The total loss is still only 5%.