So I reran 11-1 just to see what's in there since completing it I never looked back, and I just cleared it again with all pest encountered. If this helps, I ran the map without changing anything and with slow squads(420-540 speed), the helper is faster than my 1st squad. But it seems that the real major problem in that map is RNG and if it's the case then my above advice will be just a little help or not at all.