Sorry for the late reply Stur, long day at uni non stop today *sad face*. Dalamar pretty much summed it up in short.
Are the bell/furnace classifed as a warmachine btw? If so then you can deal with it using purple sun and pit of shades. Otherwise I'd just ignore the unit altogether. Get a stubborn character in the side and hold it up till you've dealt with the rest of the stuff. I believe the bell makes the unit unbreakable so you can't go kill a bunch of rats and make them run. So panic them is good, Black Horror auto panics them if they suffer a single wound. So long as you keep forcing them to take checks, no matter how good their ld is or how much they reroll, they'll eventually fail and run. Whether they run before it's too late for you or not is a different story, so you'll need to be ready to deal with them if they don't panic and flee.
Despite the fact they're cheaper than our units, cheaper usually means weaker (poorer quality). So even if they outnumber us, so long as we can kill swathes of them each turn, that's not an issue. Unlike against other armies, it's not horrendously bad to be locked in battles of attrition, they'll struggle to hit and wound us just as much. I reckon units like WE and Corsairs will do well against skaven because they have the most attacks per model in our army. Except you'll probably want to take them in smaller units like in 6x2s (or 3s) so you don't waste the damage output potential of the models not in base contact with the enemy thanks to the supporting ranks rule.
For their high ld, usually is because of a character in or nearby, so like Dalamar said, either use nuking magic which are easiest to obtain in lore of death, or run some KB buffed small units into them and KB them. Once they're gone, it'll be much easier to scatter them roaches with panic tests or a good beating in CC with our more elite units.
On the topic of spells, you can further beat down large units of skaven using spell #5 and #6 in our dark magic section. Soul Steal and Black Horror will make your opponent scramble for his pool of DD. Supportive magic like those in shadow aren't as necessary against skaven. They're weak already, there's no need to drop their T further, or make our models hit at S8 using mindrazor, it's just over-killing things. Going for an aggressive stance will be better in this instance. There are exceptions, like Rat Ogres and Aboms, but I personally don't feel it's necessary to waste valuable spell choices for a couple of more intimidating units. I'm not sure how strong Rat Ogres are, for the last time I faced a unit of them, I just sent them chasing DRs for the whole game. But I assume a strong unit of CoK and a Chariot can handle them well enough. If not send in the Hydra too. You should also take up some defensive magic with you too. As you said so yourself, their magic is pretty nasty. If I recall correctly, there's a spell they have that perma drops your T, and if T reaches zero, the entire afflicted unit dies. That means they just have to cast it three times since we're T3 only. Then most of their offensive spells are T checks related. So be selective with what you dispel!
Doomwheels are annoying, sucks we have no cannons
I believe they're just 4+AS, a 4+ WS is a bit ridiculous. You could slug them with single shot RBTs, or use metal's signature spell that Dalamar suggested. It bypasses armor, deals multiple wounds and you're guaranteed to acquire it. Otherwise bring a unit of executioners to the fight. Ten or Twelve models should provide enough bodies to absorb its impact hits and random zaps and still deliver five or six S6 GW attacks on the thing. With rerolls and wounding on (3s?), it shouldn't be too hard dispatching them if they reach CC.
We've got shades, DRs and Harpies to protect our flanks, they can handle their pesky gutter runners easily. Otherwise our Hydra can freely pivot, you can send it running and burning those scouts since forests don't block LoS anymore. Their Assassins are scary, but I don't think they're used too commonly, I haven't faced any before, people usually invest in more slaves lol. But just keep your characters away from combat if possible. Your mages shouldn't be in CC anyway, your DL and Masters should be well armored to stand a chance of surviving them, and your CoB DH? Well come in, lets see who gets chopped to ribbons more.
Finally, RXB will be very good against Skaven. Multiple S3 AP shots, wounding them commonly on 4's is just awsome. Oh and don't forget the fire banner, bypass those cursed aboms regen. You could take lore of fire or metal to do the same job, but I believe I've listed all five lores we can take (incl our dark magic) and I don't think you'll be running that many mages lol.
That's what I'd do, do correct my way of thinking or improve on them as seen fit. I'm here to learn too, and it's very possible to run a balanced list consisting of all the attributes listed. The only thing missing in the list I'm trying now are RBTs. But I take shadow on default, so all I need to do is get Pit of Shades and signature spell then bye bye abom and doom wheels. I'm being a hypocrite I know, since I said Shadow is a least useful lore against skaven due to the many hexes and buffers in the lore. But since we're required to state what lores we're taking, I take shadow and dark magic on default, and it's just one solution I have option to. If you take death you can easily nuke them nasties anyway. If you take metal you can signature spell them, fire lore? burn them. There's a fire spell in there, i think spell #4, very good crowd control. If the targetted unit moves (even half an inch), each model takes a S4 hit. It'd be useful in keeping the bell/furnace at bay
Or you can try the new stupid idea I've got. Eighty (or more) spears with a Banner of Naggaroth inside. Deploy them in a single wide line across the board and do something spectacular. Keep five or six models in the second rank so your BSB can decline a challenge and hide at the back. See how many units you can tar pit lol.
What's mine is mine, What's yours is mine.
Now that we understand each other, lets get down to business.
Jacks -Shade
- WS 5 - - S 3 - - T 2 - - D 6 - - I 5 -
Equipment
Short Sword, MC Long Sword*, Dagger, RxB & RHB [20/10] MC Shade Cloak, 4 Throwing Daggers, 3x Healing Vials, 451C, [3]Dark Venom, [4]Unseen Chains, Food, Dark Steed- Spike
Skills
Basic Stealth, Awareness, TWF, Suithenlu Khythan, Ride
Magic Item
Eye of the Jabberwock
*Magical properties possibly imbued