Well I just had 2 units of Wardogs see off 9 stacks of Britania Warbands and Swordsmen :P

Excellent v lightly armoured enemies like Warbands - When assaulting Gaul. Germania, Britannia - never waste good soldiers. These Wardog Breeders get the numbers up fast again without the need to retrain. So cost effective and saves population use for peasant Garrisons...just use 1 inf unit for sieging, have some cav backup (General so no need to retrain again)...actually they are better at seiges as they dont just chase down 1 enemy - they got to the centre of town and kill all :P