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I've had this discussion with one of my friends, and was curious what the LO community thought about the subject.
To me, Wardancers, while a deadly unit, just pale in comparison to most enemies these days. Truth be told, there's just a few tweaks necessary that will put them back on par.
Here's my thoughts:
1. Lose Immune to Psychology, gain Immune to Fear, Terror, Panic. This will allow Wardancers to flee while still retaining the lore aspect that they are bloodthirsty and just don't give a crap. Wardancer inability to flee is one of the reasons I am reluctant to put dancers in my lists. A T3 skirmishing unit that gets caught off guard by even something as light as Goblin Wolf Riders means I probably just tanked my 115pt unit.
2. Woven Mist (ASF dance). This dance should not make Wardancers -1 to attack. When the Wood Elf book first hit, it was unheard of for a whole unit to have ASF (it was mostly just a character thing through magic items). Now, with a whole damn army of ASF troops, and several others ways in multiple armies to get ASF (banners, Corpse Carts, etc), this will put dancers more in line with the norm.
3. Shadows Coil (4+ Ward save dance). Make this an always happening permanent thing in combat only - similar to the 40K Dark Eldar Wyche close combat save. It represents how the dancers/wyches are dancing around while fighting. They shouldn't have to commit to a certain dance at the behest of attacking in a certain way (+1 Atk, KB dances) to gain the Ward Save. This leaves a dance slot open, if you're to retain four dances. My recommendation would be to keep Shadows Coil, make it a 3+ Ward Save, and give this the -1 Atk penalty. It would represent the dancers going completely defensive in their fighting style.
4. Points. I don't think a drop of a point or two is too much to ask.
With their relatively high initiative I've only used Woven Mist to negate a charge against me, it becomes a trade of between: Charge and get +1S or get charged and lose one attack that turn.
Fearless rather than immune to psychology would make a fluffworthy change with one consideration - a Wardancer character will have more magic items open to him, also spells that ignore immune to psychology don't ignore fearless. Granted they have MR(1) but still something to consider.
I think their ward save should be a little better, 6+ is rarely worth it when you're taking a unit that's usually quite small. If perhaps the Talismanic Tattoos granted a 5+ like the Forest Spirit rules then it would be quite nice - perhaps Shadows Coil could grant them an 'armour' save to represent parrying with their weapons and dodging incoming blades, perhaps that could only be a 6 or 5+ giving an extra 'layer' of defense rather than improving the existing one.
One thing I considered is perhaps they could have a frenzy dance which lasts until next round of their combat. Could be effective in battle, but if they destroy a unit they may be forced to charge into a stronger opponent which wouldn't be tactically sound. Granted there is already a +1 attack dance, so would only really make a difference if ItP became Fearless.
They are a little expensive when looking at the newer armies, so perhaps slight improvements to them wouldn't go amiss, or a drop of one or two points.
I think your idea is quite good, ive been thinking about this myself since I play HE mostly. And the ASF rule is buggin me... but I dunno if that should be a dance or like "WD strike first" is basic, and WD always strike first even if the enemy is also ASF is a dance with a penalty.
About the immune to psychologie, I think immune to fear/ terror etc is a good change. Maybe make them hit and run like the warhawks... this would represent them going berserk through their enemy ending up at the other side of the unit, where they regroup for the next round of combat.
Also, isnt our entire army based on no getting caught of gaurd?