I hope you arent serious man... The only time Warlocks were free HK's before BC was when they did'nt have Death Coil. When Blizzard made the patch that gave Locks Death Coil they were OP till WOTLK.
You must have been doing something wrong if you think locks sucked Pre BC. They were the most cried about class until Death Knights went Live.
... Locks sucked untill the patch released immediately before BC. trust me i actually play one and have done for 4 years....
Shamans were always the most cried about class pre BC. The patch released immediately before(To incorporate the changes of BC) shouldn't even count as pre BC even if it was about for a month or so.
Sure death coild caused some crying but the very reason WHY Deathcoil was given to the warlocks was BECAUSE they were THE free Honor Kill.
With a little research you can even see from patch notes that from release warlocks were buffed and buffed untill BC came out, which is for very obvious reasons(Underpowered much?) and then, EVERY patch there after contained a nerf of some sort from the very severe to the gradually more and more minor(Fixing the mistakes). Now ofcourse they're trying to improve the class again because they wen't too far about 5 patches ago, all the sell outs who played the class when they thought it was OP have abandoned it(A rather large clue as to it's current state) to play Death Knights.
I mean it literally btw, i wasn't just talking from personal opinion, Warlocks were THE least played class in the game and are now dropping down again. Doesn't take a genius to realise why.