I just came up with an idea that would solve a problem I've been having. I know a lot of people are probably bummed that it takes so long to grind mobs in 1.9, and even longer than it should on MCRPG because the mobs stack, and therefore the sweeping attack is useless. One solution would be that when you right-click a stack of mobs while holding sheers, they get split in four even stacks. If a stack has been split, it can not combine with another split stack. This would allow players to grind mobs at a faster pace, as they would be able to hit 4 at a time.
Another part that could be added to this would be if one part of the stack goes 20 or more blocks away, it acts as its own stack again. This means it can be split into another group of 4 stacks. (this would help if multiple people want to use the same grinder).
tl;dr: If you right-click a stack of mobs while holding sheers, it splits into 4 separate stacks.