the most of you know that its really hard to get Wither Skulls.
But i know how to get them faster
I played Feed the Beast and build a Witherskeleton farm,
After 30 min i got like 10 Skulls (This is not much because so much Skeletons spawn there)
then i took the Stonesword i dropped from the Skeletons and start killing the skeletons with the Stonesword
then i got 15 Skulls after 5 minutes (tested it more times)
So enchant a Stonesword and kill them with it, then you will drop more Skulls.
This isn't much of a guide. This is more of a "LOOK WHAT I DID" And then told them how to do it.
Whether you call it a guide or not I tried this on ssp and it seemed to work. Hunted down wither skeletons for about an hour with a diamond sword and got nothing, changed to a stone sword after reading this post and scored two in around 15 minutes. Could just be a coincidence though..
Please do not post misinformation on the forums.
-Drop rate is consistent between types used, only looting level affects it.
-Skulls can drop in survival, and do so at the same rate as in adventure mode.
Hmmm, I went on this server ( pvp.defcraft.net went to get nether resources for my base. Saw a fortress, after a while saw a wither skele, 1st kill i got a wither head, with a bane of arthprods 4 knockback 2. Pure luck ;D
Wither skeletons only spawn in chunks containing any size part of a nether fortress. To increase spawning rates remove as much of the land around as you can, to decrease pigman spawning, then create superposed spawning platforms 3 blocks high.
A looting sword is the only way to increase Wither Skeleton Head drop rates
The theory that they may drop faster if you kill them with a stone sword is false. I needed 145 kills with a stone sword to get my three skulls, which is higher than the average of 120. I used a stone sword because I didn't want to risk losing any stuff, so I built a room next to the spawning pad with a trench in front where the skeletons would get stuck and I would be able to strike at them from a safe distance. So I went around and got skeletons to chase me and drop in the trench. It still ended up taking me about 25 hours to kill that many skeletons, which, from what I've read, is actually to be expected. You will only get 5-10 kills in an hour due to the infrequency of Wither skeletons spawning.
Trust me, it's not worth it. Why would you do one boring thing for 25 hours?
Also, I don't think that there is a way to speed it up. You can grind for hours on end to get a Looting 3 sword, which only gives you +1.5% chance of getting a skull or you can go around and slab the area around the nether fortress to increase spawning levels inside, etc. But you're just trading work for work. In the end, doing all of this will result in the same amount of work - or even more work.
You will only get 5-10 kills in an hour due to the infrequency of Wither skeletons spawning.
I'm playing SMP on a vanilla server with my friend and our Nether Fortress spawns them rapidly. I had a max of 8 at a time. They spawn much faster than 5-10 in an hour. Although we only got 2 skulls, they can spawn at different rates and 80% of skeletons spawned in the Nether will be Wither Skeletons.
Of course! Get a Stone Sword and enchant it! Why haven't I thought of that before?
But seriously, the real way to get Wither Skulls faster that you mentioned in your post is to make a Wither Skeleton farm (well, you didn't really said to build one but you mentioned having one). Even without a Looting sword, you can get a lot of Skulls if you have a semi-automatic Wither Skeleton farm and you conditioned the area (slabbed everything else or flooded with Lava) for spawning.
Enchanting stone swords and tools in general is a really bad idea; stone has the lowest enchantability of any material and due to the low durability and damage (a Smite V diamond sword one-hits skeletons, which also increases the durability in terms of kills) you won't get that many kills out of them before having to replace/repair them.