For roulette groups, that's one of the reasons I typically only pull 2 sets of gobs to begin with. Basically to see if someone schmucks up and aggros the raptors before grabbing the third set.
The raptors are easy to avoid on the right wall, it's when when someone waltzes down the middle of the entry to that section (i.e. they have no idea) that they get aggro'd. You have to assume it as the default behavior, then allow yourself to be surprised when it goes well.
Also, as a general rule of thumb for DF groups I usually split the first section into 2 or more pulls.