AsyncWorldEdit

I suggest a plugin called AsyncWorldEdit

It does world edit actions in bits to prevent lag

The plugin description: This plugin has only one function: eliminate the lag caused by the WorldEdit! This is done by replacing the WorldEdits session with an special asynchronous one. All the block drawing is done in packages. The package size and how often the blocks are drawn are configurable in the config. AsyncWorldEdit is not a reimplementation of WorldEdit! It attaches the original WorldEdit API and WorldEdit classes and tries to fix the lags. There fore you have access to all the WorldEdit operations, and all those operations work exactly like in the original WorldEdit. So basically you get the same commands, same permissions and the same experience. In addition to that if WorldEdit team releases a new feature, fixes a bug all you need to do is update WorldEdit and AWE will do its job as usual. ~http://www.spigotmc.org/resources/asyncworldedit.327/