The first section I will be over viewing are the Lords of the Under Empire. Assuming a standard game is 2500 points, I will base my opinions off of that.
First Up"Lord Skrolk (5/10)
I give Lord Skrolk a 5 out of 10 in effectiveness per points spent. At 470 points, he is a very high priced Level 3 Plague Priest for what you get, but after saying that, he has been one of my favorite named characters to take. Primary reason:Plague Monks count as core. With him in my list it allows me to take two very large blocks of plague monks of 40 usually with a furnace in each. Throw a few units of slaves in there to fill in rest of core requirements, and you got some nastiness to work with. On the other side, one hit he took going from 7th to 8th edition is that you must use power dice to cast his awesome Liber bubonicus. For games that are competitive, I would leave him at home because there are other Lord choices that give you more for the price.
Thanqoul & Boneripper (8/10)
At 450 Points, Thanqoul and the Boneripper combo comes out to be worth each point if you calculate a greyseer to be 240pts, Boneripper @ 75 points, Up to an extra 5 warpstones over a normal grey seer, that he gets to reroll worth 75pts, +4 ward save worth 45pts, and extra spell worth say 35 pts, and throw in a chance to heal for 20 pts, thats 490pts there. Which I feel is well worth it.
The advantages with him is that he usually will always have enough power dice to cast spells, he has access the the 13th spell, and he get 5 spells instead of 4. Which is pretty awesome.
Goes along pretty nicely with the extra warpstone he has to cast with.
The only downside is that he wont ever ride a screaming bell, which in the 7th edition Skaven Rules I believe he could. Guess he got scared of heights or something. But at least he gets the +4 ward save that the bell normally would give him.
I personally love taking him, and feel he is very competitive as far as Named Characters goes. He is definitely one of my top 2 favorite Named Characters. The other is coming up shortly.
Ikit Claw (6/10)
As much as I like this character, I do not see him as competitive as some other options. But having said that, he is a very fun character to have. Bringing the beloved Storm Daemon into battle and having descent saves by himself makes him a viable and fun selection. But at level 3, I would look elsewhere.
Throw The Unclean (8/10)
Probably one of my top two favorite named characters. On of the reasons is that I love having rat ogres on the table. Allowing two large groups of Rat Ogres core (18 each), I think is a huge advantage, which can give you up to 60 attacks at str 5 for each unit.
He is also pretty cheap compared to other Lord Options which will allow you to Add in a Grey seer if you wish. Additionally I enjoy the fact that he 4 attacks that are considered to have creature killing blow, and then an addition whip attack that can lower opponents ld by 2.
And if all that is not enough, he also enjoys having the blessings of the horned rat by having regeneration.
Queek Headtaker (7/10)
Probably one of the most underated Named characters as he is the only one that can buff up Storm Vermin by giving one unit of Storm Vermin +1 ws and +1 str.
As far as Skaven Warriors goes, he is pretty descent in HtH combat, and does even better in Challenges as get he gets both a +1 to hit and to wound. His armor is pretty descent as it gives +3 Armor saves at the same time bounces back successful hit with a str5 hit back. Thats pretty dang cool. I have played with him with great success mainly because of my large block of Storm Vermin just kick butt.
Ohh how much I love playing the vermin lord, oh how much a target is painted on his head. Luckily he has 5 wounds, is a fighting machine, and can cast with the best of the skaven. He is much better with the 8th edition rules than the 7th edition rules mainly because of how Terror works. Plus Large Target doesn't give bonus to people shooting at him. For Fun games I think its all right to take him, not too much cheese because he is easyily snipable, but, he does pack a punch and miscasting the 13th spell doesn't bother him too much as he isn't by any of his own units, and he does have those 5 wounds. That is if he isn't instant killed. Another knock on him is he only has a 5+ ward save, which isn't that great, just like any other daemon out there.
The first of the non named characters. The warlord has many options you can go with.
First option is what some call the butcher. Basically getting on the warlitter, taking a shield and warpstone armor, giving you the +2 armor save, with back bounce damage. Very good against rank and file units that have low str. The next setup i have used is the flanker setup. I put him on a Rat Ogre, give him the warlock augmented weapon, portents of verminous doom, and the warpstone armor(which of course I love to put on him) This setup is basically for hitting the flanks of armies and making them run. Put him in with a group of rat ogres, and not much can with stand a flanked charge from him, especially having that portents which lowers enemies' LD value by one. This setup also gives him 10 Str5 attacks (including the bonebreaker). Very nice I think. Another setup I have used is the bounty Hounter. Basically Give him a shield, great pox for movement, and the fellblade. You can then have him join a fast moving unit if you like, but basically aim him towards anything scarey on the opposite side, at let them have it. I have done this once, killed two dragons before the fellblade finished him off. Luckily in 8th edition you can have more than one lord under 3k.
Overall I love the warlord options, and there are many more. Very good companion to the grey Seer, and should be considered for every list.
If you do not have a grey seer in your list, your probably playing for fun, or have some other really cheesy option out there. The grey seer is one of the best options for lord, if not the best. Coupled with the power stone, you can almost guarantee that he gets of the 13th spell which can be a huge game changer. Also give him Skalm to heal any damage from the miscast that could, and probably will happen. The Bell mount he has options to is also a very solid choice, and has the fun factor and competitive factor rolled up in one.
If for some reason you find your self having two of these guys in your list, and you can always have fun with skitter leaping into the back ranks, then miscasting your 13th take not just the average 14 models with that spell, but also have a chance with a large template surrounding the grey seer, and kabooming it. I have done this once, and the look on my opponents face was :(
Loved every moment of it. Grey Seer is a very competitive Lord, and should only be really considered if you aren't really concerned how the your opponent feels about cheese and sportsmanlike conduct.
(PS. On the grey Seers, the only items you really need to take is the skalm and power scroll, everything else can be taken by a caddy)