This comment is for PvE reasons alone, not PVP, but lets talk somewhat about balance.

Currently, the pre TK/SSC raid spec is affliction all the way. And this is also the defacto raid tree, as it holds several raid buff/creature nerf talents like malediction and Shadow Embrace. A well balanced raid should have 2 warlocks with a deep Affliction spec to be optimized for debuffing/buffing.

However, in SSC and TK, Blizzard sees the need for a warlock tank in two encounters, something that forces at least 1 warlock to spec into Soul Link, a worthless talent for raiding, expect for those 2 encounters.

As if this forced respec for a warlock was not bad, we have the problem of itemization after Karazhan.
Zul'Aman, Tempest Keep, SSC and Black Temple all focus on Crit and Hast along with Spelldamage. For a affliction lock (remember, the blizzard designed "raid tree") crit and hast does not buff damage at all. Shadowbolt is around 30% of the damage done by a affliction lock, so hast and crit is not a good investment to up damage.

So, if a warlock wants to spec for raiding after Karazhan, you need to spec deep Destro, but Destro is not raid friendly, as it has no Hit talents, and no raid buffing talents. However, it's the only tree you can go if you want to benefit from anything that drops.

So there is a need to look at warlocks and how they work in PvE, as it's currently not working as it should.