Have seen this too. 

However with the appropriate hero + units combination and spells, they should not pose a problem. For example with Peregrin with the shoot-first-ask-questions-later-skill, and 3-4 archer units, all the weak units should disappear. And with some (Kraxis) Lancers and slow both Vethy and Alzy is a piece of cake. 

Besides you can see the units in the army, and arrange your army to counter these units. For example Vethy is quite quick for such a large fellow, so be sure to have some canon fodder and some slow / area of effect spells (Blizzard is a good bet), a lot of high damage units etc.