Sure, I'll give it a go. Not particularly familiar with artificers though.
Well, flavour, prerequisites, and skills seem to fit.
Seems to fit for helping the unarmed combat part. That said, you don't actually make the fist of constructed levels stack with monk or unarmed swordsage for determining damage, which it is implied you intended given your mention of them not getting the damage increase if the combine levels would make their normal damage higher. You also forgot the 'd' in swordsage.
Three things, first, you should note if there is a duration on how long you may keep an infusion dormant on you. If not, you should note if dormant infusions count against your infusions per day when cast or when activated, and if when cast, that they automatically expend infusions of the appropriate level when you take 8 hours of rest and would regain your infusion slots (so as to avoid things like applying all your remaining infusions as dormant ones before resting so as to have more than your normal daily allotment).
Third, while I'd expect you may only activate a single dormant infusion at a time with a swift action, that isn't entirely clear.
A nice ability.
The wording on this could use some work. It might be better to say:
At fifth level, the dormant infusions may be expended for defence. As an immediate action, you may activate any number of dormant infusions you have. However, instead of gaining their normal benefits, you gain a bonus to AC and an amount of DR/- equal to half the combine spell levels of the infusions you are activating. These stack with other sources of AC and DR/-. These benefits last until the start of your next turn.
Another nice ability.
Fits the theme of the class well.
Useful, though probably not overpowered.
As the above.
Might be useful to specify how this effects the casting time of infusions that are not of the mentioned casting times. Other than that looks good.
Now to finish reviewing the dances from Dancer of the Threshold:
Nothing wrong with this that I can tell, though rather fun, and flavourful with the Perform (Dance) bonus.
This sentence seems to need slight rewording. Most likely able to be accomplished by removing the word 'effect'.
Given the next sentence states the spell must be of a lower level than the one countered, you could remove the part mentioning it specifically with regaining a spontaneous spell slot.
Seems fine, but both of the paragraphs have random enters in them.
First thing to note, should say 'effects' in the first paragraph quoted rather than effect. In the second paragraph you again have a random enter. You also should remove one of the two spots it states buried undead will automatically try to dig out of the ground.
Should say 'radius of 5 feet'. Also, another random enter.
Seems fine, but another random enter.
Good ability, but you tried to close the italics with a [/b].
Minor typo, but die is singular, you should use dice there. Otherwise looks good.
Edit: Also, added a more noticeable capstone for the Sower of Strangeness. See Seed the Land ability for details.
Owrtho