Honestly, Warlock is one of the easiest classes to get Silver on. Sorry to hear it's been so problematic for you.
That's a bit odd. Silver is so hard for Balance Druids there's actually posts detailing the strategy of how to get it. (Because Balance has a single interrupt with a cooldown longer than the time between interrupts, and extremely piddly burst AOE.)
Since 6.0, Proving Grounds scales the mobs to your ilvl. Something you'll notice quick if you go in for a tank test and try to no-CD it.