Sometimes, you have to go with stupid setups. I was playing a games useing other guns that I know are worthless (flamers, barriers, machine guns, poison, boomerangs, etc) and found the ants were looseing the typical congo lines they adopt when crossing areas the poison cannons were infecting with the "you can't build here" bug.
I played a few games with poison towers strewn around the map (usually 5 set up with 1 in each corner, one int he middle so that the ants were always poisoned), and they tended to wander all over the map like they do in the level 100+ games with only 1 pice of cake left,only they were doing it in the lower level 60's with nearly a full cake. Even the ants with cake woud wander back and forth accrost the map instead of heading straight(ish) towards the hole.
I've not done enough testing to see if it was a fluke, or there's something to it, but it would explain why some less experienced players like the combo of ice + missles + poison. (without the right setup, and without this actually being true, ice/snipers or to a lesser extent ice/quicks will still completly dominate a ice/missle setup).