Thanks for feedback. TBH I gave giant rats similar unit size as squig herd, because I thought they fill similar role, but you're right, they're weaker.
I've decided to create Skaven minion rules for AoS Solo campaign. Boss behaviour table is mostly a reskinned Gloomspite Gitz one. Warning - not playtested!
I've changed D6 (as published in WD) to D3 in boss chart as it was definitely a mistake.
AoS-Solo-Skaven2.0.pdf