Playing rats is always dangerous, that's why the linos are so cheap. But they are also very useful with AG3 and MA7.
My advice:
Drop the Rat Ogre. Get him later. He is too expensive, and a liability on a new team. Max-out on the GRs.
The Linerats are to be used to put TZs on important opponents. They protect the GRs, by putting TZs on opposing blitzers and other dangerous dudes. They will get smacked, but they get back up and put a TZ again. They will get injured alot some games, but you will be amazed on how resilient they are. And if you play your GRs right, your opponent will be too busy doing risky plays to get to your GRs and will often not even get around to hitting your linos.
Skills:
Linerats: First skill is Kick. Skaven and Wood Elves are the two teams who benefit the most from this skill. You kick deep, then put pressure on the ball retriever before he cages-up. If nothing else, you can slow down the cage from forming, hence not allowing for enough time for your opponent to score. Next skill is block. Again, these guys are used to mark your opponent, and block will help with that. I would not give these guys fend. They are there to put TZ on people, not to stay away from them.
Blitzers: Tackle and Guard are the first skills for these guys. Which one you pick first depends on your league. Doubles: Horns I like a lot. Great for punching holes.
Thrower: leader is good, so is block depending on your reroll situation. I use my thrower as a glorified line rat. He gets in the thick of things when needed. When you think you can get the ball lose, he can be used to pick-up the ball if there are no GRs available to do so. In my team, he is more of a defensive specialist.
GRs: These are, obviously, the stars of the team. Two get block then side step. These guys are great on offence and on defence. They will quickly become the most hated players around. One gets wrestle and strip ball. Then leap if you can. He's the one who blitzes the ball carrier. Keep a reroll around, block with two dice opponent choses. All you have to do is not roll a skull, and the ball is lose. Works way more often than you would think. Although don't go jumping around in cages all the time. Make sure that you have somebody around to pick-up the lose ball. The fourth GR: I like Big Hand and leap, and also Two Heads if you get a second double. Once the ball is lose, you can leap in, pick-up on a 2+, then dodge out and pass to a blodging sidestepper standing close-by.
Rat Ogre: Juggernaut and Break Tackle. A smart opponent will mark him with line fodder. Break Tackle allows you to get him out of there and use frenzy with juggernaut to crowd surf, destroy a cage, or whatever else. Prehensile Tail is golden against dodgers, so just standing next to the ball carrier while avoiding 1 or 2 dice blocks against him is pretty nasty.
Blocking: With rats, I block only when there is a tactical advantage to do so. Usually this means punching a hole such that my GRs can get through. This means that rerolls are rarely used on blocks. Don't start a blocking war unless you are playing WE or Elves. You mention that you want to go toe-to-toe with Orcs and other meanies. Well, I wouldn't. If you do, let us know how it went.
Scoring: GRs can easily score in two turns. One GR stays back as ball retriever, the 3 others can flood one side of the field. However you do it, it's easy to score (usually). But try not to score too quickly. The key to beat Skaven is to manage the clock. If you can, take time to score. Obviously you will not be able to hold-on for 8 turns, but try to take 3-4 turns to score. Then with the kick skill and your GRs applying pressure, it will be very hard for your opponent to score in 4 turns.
Defence: The most difficult part with Skaven IMO. With the kick skill (did I mention that this is the most important skill for you team

), kick deep. Apply pressure with GRs and Blitzers. Your opponent needs to take care of the blitzers as they have block and are ST3 (with Horns if possible), which may leave a couple of GRs a bit more free. Try to pop the ball lose. With the above skills on your GRs and Blitzers, it will happen fairly often. If your opponent manages to cage-up, then you can either stall the cage, which could mangle your linerats, but often works. And if you lose some rats, who cares. They are cheap, and you get journeymen for you next game, which are excellent on the LoS. Just don't get attached to your linerats. Always keep a GR in scoring position. Wait for the opportune moment to attack the cage, using a combination of Horns blitzer, blodging sidestep GRs, wrestle strip ball GR, and if you knock the ball lose, get the leaping Big Hand GR to grab the ball and get it out of there. You can even just throw the ball as far as you can without fumbling. You have a good chance of getting to the ball before your opponent does in you next turn if you are positioned right (with the GR in scoring position).
Rat Ogre: Good purchase, a bit later. He is good, just too expensive on the starting lineup IMO. He is there to crowd-surf people, to break cages, and to put his tail on opposing ball carriers with dodge. He is a bit fragile and it can be hard to provide support for him, so be careful that he doesn't end-up in the middle of a bunch of Claw/MB Chaos Warriors or the likes of them.
Well, that's how I play them. High risk high reward GR plays. Keeps your opponents on their toes, makes them get off their game plans, and causes havoc and turnovers. And its darn fun
I also find it interesting that you are saying that Skaven will more of a challenge to win with than Chaos. Chaos are quite hard to play with early-on. They take many games to beome decent at anything. Skaven are scoring machines. IMO, it is much easier to win with Skaven than it is with Chaos.
But to win, you have to play the Skaven way. If you play the Chaos/Orc way, then your team will become pitch fertilizer.
Hope this helps. And good luck.