Why go for the Coven Patrol? If you just want the Grots, save the points and just go for the Auxiliary. 5 wracks and 4 grots are not going to do much, even at 1000 points. However, one big blob of grots would be difficult to deal with. 1 CP to roll those Haemi/Wrack points into more Grots would be worth it IMHO
Thats my $0.02 anyway.