QQ or QQ more/moar is a common mnemonic (not limited to Guild Wars) for cry more. The two Qs resemble a pair of tear-filled eyes, which is commonly and erroneously claimed as the source of this definition. It derives from old text-based dungeon crawlers where when people "rage quit" by hitting alt-q several times, people in channel would see several "q"s. This was later just shortened to qq to make a light suggestion to (or not to) rage quit.
The use of QQ is generally a part of a rebuke or reproach. Its use is typically derogatory and dismissive. It is targeted towards players perceived as whining about gameplay mechanics or other players, instead of effectively using the tools at their disposal. It is common in both PvP and PvE communities. In the PvP community, it is a staple of all discussions involving builds and nerfs, and in the PvE community, it shows up often in discussions about farming.