You are not forced to use Viking Units....

[Fatt_Shade]

@Loopy

Also important to consider is equipment and spells. Consider that Bless will improve non-crit damage by 50% on Thorns but only 8% on the Dragons. Crits improve damage by 300% on Thorns but only 62.5% on Dragons. Equipment that adds +1 damage will add 33% damage to Thorns but less than 1% damage on Dragons.

That`s why said many things come into consideration regarding dmg/lds ratio to units.
As you said when you reach +60 att on enemy def there is no more need for frenzy and bonus att, then pugmy/plague means much more then +att item, or using +dmg items instead some pure +att equipment.