I'd have to agree with Dark Pact, once you learn to use it (which doesn't take that long) it becomes invaluable to Affliction - Grind, PVP, 5r or Raid.
Also, I'd have to say that Supression is a better tech than Contagion for you right now. In BG and WPVP setting out random DoTs on your foes will rack up your Damage count like crazy, and will definatly help with some Honor and help your team. To actually kill someone, however, you need to actually focus on them and use your fiendish 1 on 1 skills such as Fear and Drain Life.
Here's where Supession takes a jump ahead of Contagion. The damage % is negligable, and while the 30% anti-dispell is a very very worthwhile attribute to your Fliction spells, in this game of 1v1 you're going to be relying less on Resisting dispells and more on resisting the spell in the first place.
You're build is very much in sync with what I had at that level bracket, but If I were to make a suggestion to you it would look a bit more like this.
Fliction Lock 49 Build A final note here - While Drain Soul is a relatively low DPS spell (if you have a good wand at 49 you can outdps it with wanding) when combined with your DoTs and especially when you have multiple people beating down on your target, the 15% Manapool restore is a crazy powerful effect in any situation. You may want to roll with 2/2 Impr Drain Soul, but one can definatly argue it's just another way to get mana added into an already long line of techniques.
Also, Empowered Corruption becomes one of the best talents as your Lock reaches the very highest end of the game, but at this level this is really going to depend on your gear. Looking at your gear I see you have a good enough amount of +damage and +shadow to make this work, but this brings into question your low Stamina and high Intellect. Bit of an odd gearbuild you have there, although very good -- don't get me wrong. Almost looks like a Destro gearset, though.