It depends on how you would define counter insurgency here. Based on skillset, I'd say the Catachans are a clear winner here but IMO they wouldn't be as effective as say the Athonian Tunnel Rats when placed in an urban setting. The same would hold true for the Tallarn Desert Raiders if it were a desert setting. As for the Mordant Acid-Dogs I'm a bit unsure how to place them. In my head canon they act more like a "zone mortalis" type of army, one you wouldn't hesitate to use in a blasted/toxic wasteland and one in which the achievement of the goals trump whatever losses in manpower incurred.