Skaven are one of the top armies right now; they have strong allegiance mechanics but IMO the main reason is simply that do many of their units are too few points for what they do. Looking at your list you have, either intentionally or accidentally, hit on some of the best units. Plague monks are among the best units in the game due to sheer offensive power verses cost, clanrats are simply dirt cheap for tons of bodies, the vermin lords, bell, furnace, and thanquol all got a 5+ fnp (effectively a 50% wounds increase) without their points going up. Thanquol is probably the weakest link in this list by virtue of how many points he costs, but at the same time his warpfire is a valuable source of anti-horde for the list and his command ability is likely to be useful.
The strongest thing to do would probably be to pull Thanquol out, bump the 20-man clanrat units to 40s (a 40-man is more than double the effectiveness yet costs less), and put in a Vermin Lord Corruptor for his warscroll spell, plague-monk buff capacity, and generally being ridiculously good for his cost. Give him the Sword of Judgement artifact (from the Malign Sorcery supplement) for trollolol hero/monster killing capacity.
But depending on your local meta what you have may already be too strong, potentially way to strong.