If we have a castle and 2 Barbarians, we need to build 4 GMs. If we only have 2 Barbarians, then build in the Barbarian dwellings.
And regarding the "oppression," it's even simpler. 500 Galtaran skeletons on day 2 also result in a significant "oppression"! And 4000 MP from a bad Kirie... In Heroes, there's "oppression" everywhere; in the end, everyone is in equal conditions.
P.S. :)

"Это нам идеально подходит!" [Новосибирск, 2013]
"Красавчик! Если только не читер.." [Киев, 2014]
"Это Вам не шутки - нажрался Dust в маршрутке" [Новокузнецк, 2015]
Сам ты фиш (с) :D