Ok, first thing to note is that, if it's a tournament, you almost certainly won't get away with being 13 points over, or even one point for that matter, so make sure you stick to the limit.
Secondly, like thedarkavenger points out, your units are too small. Generally in Fantasy, bigger is better for infantry units, so your Corsairs and Executioners could both do with being bumped up to 30. However, you're not going to have the points so, since Corsairs fill a similar role to Witch Elves, I'd drop them altogether. The flaming banner will serve you well against any HPAs you might encounter, but I think you'd be better off with a Fire Mage, BoEF Xbows or simply poisioning it to death with your witch elves.
Executioners are a good unit, but their strengths don't come in terribly useful against Skaven. You're better off dropping them for a unit of Black Guard (dropping the Corsairs as well should give you enough points for a unit of 20 or so with the Razor Banner), more
RBTs or Warlocks or even another Hydra. The latter is perhaps not the most competitive choice (I think Black Guard would be best) but flaming breath attacks are always good against Skaven and two Hydras plus a CoB should be enough target saturation for any Warp Lightning Cannons you encounter.
Next, you need to sort out your Magic. I personally think that, if you're taking a Lvl4 Dark Magic Sorceress on a Pegasus, you may as well take Morathi, since she does exactly the same thing but better, and the extra bonuses she has are well worth the points increase. Dark Magic isn't the best lore, but it is still very good and I think it would serve you well in this list. If you can get any practice games in beforehand though, it would be worth playing around with it. For your Hero Sorceress though, I'd recommend downgrading her to Lvl1 and switching to Beasts. Shadow is a great Lore, and synergises beautifully with Witch Elves, but you really need to be a Lvl4 to get the most out of it and, furthermore, it isn't of huge value against Skaven. Lvl1 Beasts, on the other hand, guarantees you Wyssan's, which is a fantastic spell for Witch Elves. The extra points saved could also come in very handy.
Finally, as a few nitpicks, drop the Full Command on the Dark Riders (you only need a musician) and get Witchbrew and, if you can afford it, an Ogre Blade, on your Death Hag.
Hope this helps, if you have any more questions, feel free to ask!