Grudge Marks are ridiculous

Arena of Fortitude on Champion last stage with a boon of harmony turning THP into HP and full team with good talents. It was Khorne and we got Blood Gods Fury. A Troll spawned, Vampiric Illusionist Rampart. We could not kill it, it vomited everywhere ahd its health was always 100%. Enemies spawned constantly, a LOT of Warriors, Marauders and Stormvermin. We literally couldnt killed it and wiped, we play on Champion to avoid this kind of retarded bullshit on Wastes, what the fuck were we supposed to do? Please fix this Fatshark this is terrible.