For most players, rushing is easier. I've seen teams TRY to clear and wipe instead. Hell, I've seen them try to rush and wipe. Try to tell the bears or even the birds to stun the sniper/berserker and see if they do it. The answer, mostly, is NO. Amazing, no?

For good players, it's faster to clear. Wiping gathered+stunned mobs is pretty simple and it protects the team should anyone die later or accidentally steps through a portal when it appears.

I need to note down all the clearers. Haven't really played in almost a week so I'm not even sure who's on anymore.