It sounds like you may be mistaken about skills and accuracy. There is no gen skill to reduce boss damage, but Vargus lowers all enemy damage by 5%. So the Wolf's damage will be 4750-5700, and with 50% accuracy this means that 50% of the time he will hit for exactly 4750 damage, and 50% of the time he will hit for exactly 5700 damage. There is no in-between (accuracy always works like this).
The key to a clean win here is making sure you kill the camp in 2 rounds. Because the Wolf is last to be killed in this situation, if he survives to the 3rd round his first strike damage will finish off the MS and take out a big chunk of AM, possibly wiping the whole army. If you cannot get a clean win in 2 rounds, you should suicide just enough knights to kill just enough frost giants so that you can finish it with Vargus in 2 rounds. The suicide general you use won't matter much since the frost giants have such high hp (i.e. even Nusala can only kill at most 3 of them herself, the rest is up to the knights).
It is very important to have all the correct buffs/debuffs from the previous ventures active while simulating. Note that the EvilJ link you cited is a version with 0 combat debuffs and 2 combat buffs active during Giant Battle based on the entire "CoA Skills" version of the chain. I just sim'd it and it works.