Well then, lets see about your class. First, I'll note I quite like the concept. It's always fun to see a dancing based class, and necromancy is one of my favourite schools of magic.

Quote Originally Posted by JoshuaZ View Post
Skills: Perform(Dance) 8 ranks, 2 rank in another Perform skill, Knowledge(religion) 2 ranks, knowledge(arcana) 2 ranks, spellcraft(2) ranks
Well, first thing I noticed, on spellcraft you seem put the ranks in parentheses, while not doing so for the other skills.

Skills seem fine, they match the theme of the class.

The spellcasting progression makes me a bit wary, but seeing as you need levels in a different class from the one being advanced (even if it is a class with minor progression of its own), it may be fine.

Bardic music usage advancement fits fine.

Quote Originally Posted by JoshuaZ View Post
Dark Lore(ex):Dancers have deep understanding of the darker aspects of the world. They gain an ability functions like the bardic knowledge class feature with their Dancer level as their effective bard level. This ability applies only to knowledge about necromancy, the undead, or other morbid or macabre subjects. If the Dancer has the bardic lore class feature or some similar feature from another class, the Dancer levels stack for issues that Dark Lore would apply. So for example, someone were Bard 2/Wiz 4/Dancer 1, their effective Bard level for information about an ancient undead lord would treat their bard level as 3, but a question about elven archery would use the default bard level of 2.
Nice and flavourful. However, it seems you are missing the word 'that' in the second sentence.

Quote Originally Posted by JoshuaZ View Post
While dancing, generally you may take no more than a five foot step, but may take any free actions as usual, and may take one move action. You may not take any other actions except as where noted.
This line doesn't quite make sense. Might want to clarify it.

Quote Originally Posted by JoshuaZ View Post
Similarly, a too much Dancing on a single day can be tiring. If you danced more than your three times your class number * your con modifier rounds (minimum 3) without having had a chance to rest
for at least 8 hours then you must make a fortitude save each time you begin a Dance equal to 5 + the total number of rounds you have Danced since you last rested above your normal Dacing limit (3 * class number * con modifier).
Just some minor typos, but you need to remove 'a' in the first sentence, and should change class number to class level in the second.

Quote Originally Posted by JoshuaZ View Post
The save DC for any Dance is Ranks in Perform Dance + charisma modifier + dex modifier.
Don't see any real problem with the non-standard DC.

Quote Originally Posted by JoshuaZ View Post
Unless stated otherwise, the effective caster level for a dance that mimics a spell is equal to your number of ranks in Perform(Dance).
I'd suggest stating this can't exceed your total level.

Quote Originally Posted by JoshuaZ View Post
Due to the obscure nature of Dancers' magic, they are difficult to recognize. To recognize that someone is engaging in a magical form of Dance, one must make a DC 20 Spellcraft check (people with at least 2 ranks in Perform(Dance) get a +2 bonus on this check.) A Dancer of the Threshold automatically succeeds at this check.
I might suggest making the bonus require 5 ranks in Perform (Dance) so as to better match with other skill synergies.

Quote Originally Posted by JoshuaZ View Post
Dueling Dance (su):
... Each dance for a round, marshaling your necromantic power through your dance
A Dueling Dance dances may not have any benefit from others, such as assistance from backup undead dancers.
A fun ability, if not one likely to be used often. Might be worth expanding it in some way to be usable with willing non-dancers. Anyway, a few typos. The first sentence above should either start with 'they' or have an 's' on the end of dance. The second I'd recommend changing 'dances' to participant.

Disciplined Mind is a nice flavourful ability.

Sense the Opening Door is an interesting ability. Given the flavour of it, it may also be fitting to at some point grant an ability to easily identify creatures as living, non-living, dead, or undead.

Quote Originally Posted by JoshuaZ View Post
Smooth Movements (ex):
At 3rd level, on rounds during which you have initiated a Dance or continued any Dance.you get a +2 competence bonus on all reflex saves and to AC, this becomes +4 at 6th level and +6 at 9th level.
I'd suggest altering the wording to be since the start of your most recent turn, rather than during rounds. Mainly as it currently does not grant the bonus at the start of rounds before your turn arrives in initiative order if you started or continued a dance the previous round.

Quote Originally Posted by JoshuaZ View Post
Death Knows Her Own (ex):
Additionally, Dancers may automatically recognize if someone who is dancing is undead.
I might suggest altering this to letting them recognize undead while dancing. As it is, most undead are unlikely to dance. Perhaps alter it to granting the effects of the deathwatch spell while dancing.

Last Dance is an interesting capstone, and while powerful, doesn't seem problematic given its ability to only be used successfully once.

On Age Draining Waltz, I'm not sure the use limit on specific creatures is needed, given the time required to pull it off. Then again, I may be slightly biased with regard to that, as the limit prevents the interesting idea of a Dancer dancing with someone as they gradually get younger, while the other person gradually gets older, until the ageing person eventually dies.

Only skimmed the rest of the dances, though I'l try to look them over in more detail later today. That said, it might be worth adding a feat that allows you to learn additional dances you qualify for, possibly with the prerequisite of already knowing 9 dances, or noting dances learned by the feat don't count for learning other dances. This was a Dancer may continue advancing their dances after reaching level 10.

Quote Originally Posted by JoshuaZ View Post
Regarding your class: It is really well done, and combines two really neat homebrew base classes that deserved to be combined. The total set of class features seems small, especially the last two levels. Lots of class features depend numerically on the class level, so this should't be too bad. But something at 10th level would still seem to make sense. An obvious ability for 10th level would be something that made it so that levels of other classes and PrCs which advance grafting also count as ozodrin levels for purposes of total Form Points.
I'll admit, I did have some trouble trying to come up with a capstone. Initially the implant seed was going to be it, but then I decided that should come sooner. I though the ability to grant others the ability to make seeds and graft them for you might cut it, but it is rather situational. Perhaps I could add the idea I'd had for a feat that would let you graft your seeds onto inanimate things like plants or walls as a capstone. As for the class features depending numerically on class level, I'd thought they mainly were based on the total graft level of seeds hosts had on them. Odd, I'll take a look at that.

Quote Originally Posted by JoshuaZ View Post
Also, it may make sense for Strange Bonds to be (Su) rather than (Ex) given what it does. Feels more supernatural than extraordinary.
Hmm, your right, the ones that mimic spells should likely be supernatural. That said, the others are more intended to show that the grafts are a part of the sower still, and as such have some connection.

Quote Originally Posted by JoshuaZ View Post
Sense Seeds may need to specify the level of accuracy that one gets for the distance and direction. Also, what happens if the target is on another plane?
Well, as I see it they could generally point to in the direction of a seed and estimate about how far it is (depending on their sense of distance). As for if the host is on another plane, I should specify that. They may tell what plane the seed is on, but not what distance or direction it is (and they don't actually know the name of the plane unless they've been there, or know it from another host of a seed going there, then coming back and telling them what the name was).

Quote Originally Posted by JoshuaZ View Post
Shadow is a proper noun here, right? If so it should be capitalized.
Gah, missed that. The Black Forest should be capitalized as well. I'll see to fixing it.

Quote Originally Posted by JoshuaZ View Post
I'm not sure I'm parsing the second sentence correctly, but I don't understand what it means. It seems like a very roundabout and awkward was of saying that everything can easily kill people. Maybe you mean something like "It is said that every living thing there is capable of killing a normal man with ease, even things like squirrels."
I suppose it is somewhat roundabout, though I'd not really noticed it. I was somewhat thinking about it more like locals assuring people there is nothing that is safe to be near in the forest.