I created an archery / ninja to see after reading this thread and another similar. Got her to 50 and T3 on some incarnates, just to make sure that I am assessing her fairly. Conclusion: Archery is good but /ninja makes me sad that I didn't get a better secondary like /tactical arrow or /devices (or any other)
She's so bad compared to my main blaster (beam rifle/devices) that I've stopped playing her. I might make a second archery blaster even though I nornally never revisit a set I've played, because it was so good it almost compensated for ninja's weaknesses.
The major issue I have is that it doesn't convey a ninja play style. The lack of decent build up means that the initial burst damage is very poor. I don't know who thought the build up mechanism was a good idea, but it doesn't work well solo and it doesn't work well with teams. The low damage of the secondary attacks makes them 'meh' to use: I could have shot them with an arrow instead of wasting my time with the sword. The level 2 confuse / sleep was laughable.
I also played a /ninja sentinal. And ... wow.... /ninja on a sentinal is fantastic. I was only defeated three times getting to level 50, and two of them were because of the team I was in. It felt like a ninja, it exemplar's fantastically well and was a joy to play from beginning to end.
I think there is a case being presented that 'there are secrets in here that are not obvious that make it good, and I'm not going to tell you them'. Sadly I tried to find those secrets and failed. Perhaps that's because I am a rubbish player, but on the whole I would recommend to people that don't want to nerf themselves that they should get a better secondary (almost any other)