I ran randoms all day today by myself. Most of the time I was 30 kills or more, and many times I had 0 deaths. If you play it right Deception assassins are great. You just need to pick your battles. I used my vanish quite often, it is there for a reason.
I do not even have full pvp gear. I still need four or five pieces. Also this is without using any of my buff CDs. I never used them once, not all day. Mainly because I always forget to use them in the heat of battle.
Deception is fine. They could use better survival CDs because we do take a huge amount of damage if focus fired, but then again you won't be focus fired a lot if you know what you are doing.
Single target I can take down people a lot faster than darkness can. At my current gear level I have four abilities that hit for 3k+ a hit, and when I go through battle properly I can unleash them all back to back. Usually only those who out-gear me by a lot have a good chance of beating me. Even then I can put a huge dent into them.
I am also one of the rare few who do not charge-swap. I keep surging charge active 100% of the time. Could I do better with other? I could, but I would rather get used to the proper mechanic of a deception assassin.