The primary problem I see with Assassin DPS is that is is too proc heavy, and that our resource penalizes us for bad luck. You can go entire fights without any primary dps procs. You can also go entire fights proccing every hit (But our resource pool only supports 1 proc per 5 seconds).
What you end up with at 50 is a sort of 'capped burst' system where on average, you have steady dps over time(great for pve), but in pvp you range from 'decent' to 'very unlucky'.
If you want to do dps, there are better classes for it, that are much easier to play. If you want a class that does a lot of things well and directly scales with how well you play, Assassin is a great choice.