I've had a concept in my mind based on the Wardancers of the Warhammer Fantasy Wood Elf army, and wanted to just slightly increase their mystical nature (Ie: some spells, in addition to their enchanted blades). Since they are dual-wielding types I was bending over backwards trying to create a multi-class fighter/wizard(or sorcerer) creation when I finally just decided to hybrid them, and the more I hybrided them, the more Magus they seemed... so I tried an Archetype instead. I -think- it's balanced, but would like some input from others, since I've not played anything like a Magus in quite a long time (Not since the Kineticists came out). Tried to take away more than I added, but not sure I'm objective enough on this.
Elven blade masters are a group of noble born warriors of Xoth Sarandi, trained in both the martial arts of the blade as well as in the mystical arts. The difference between them and other members of the Magus class is that they see the weapon as the tool of the martial aspects, and keep it separated from the mystical aspects of their training. They use a pair of blades and perform katas that appear almost like a dancer, allowing them to flow through a battle much as water flows through a sand barrier.
Class Skills: Elven blade masters gain Perform [Dance] (Cha) as a class skill. This modifies the class skills of the magus.
Diminished Spellcasting
Due to their martial focus, they do not learn to project spells towards living targets, and instead focus most of their spell casting on themselves. When generating the Difficulty Class to resist a spell, the elven blade master always treats her intelligence bonus as 0.
Arcane Pool (Su)
When calculating the amount of arcane points in his pool, an elven blade master uses his whole level rather than half his level, however when using the reservoir of mystical energy to fuel and enhance his weapons, he must spend 2 points from his arcane pool, but gains the benefits onto both of his weapons when doing so. This ability modifies the arcane pool ability of the magus class.
Two Weapon Fighting (Ex)
Elven blade masters start the game with the Two-Weapon Fighting feat as a bonus feat, however, she must meet the requisite of the feat to gain the benefits the feat. This ability replaces Spell Combat.
Two Bladed Defense (Ex)
At second level, an elven blade master gains +1 shield bonus to her AC anytime that she is wielding two light bladed weapons, and wearing light or no armour. This increases by another +1 every 5 levels after 2nd level. The elven blade master may spend one point from their arcana pool to add the enhancement bonus of a single weapon they are wielding to their AC. Note: this is an enhancement bonus, so would not stack with the enhancement bonus of magical armour. This ability replaces spellstrike, medium armour and heavy armour.
Magus Arcana
At third level, the elven blade master gains the dual bladed magus arcana automatically (See below), in place of the Arcana she would otherwise receive at 3rd level. This alters the magus arcana ability of the magus class and replaces the improved spell combat as well as the greater spell combat of the class.
Bonus Feats
Elven blade masters do not gain the bonus feats that other members of the magus class receive, rather they receive Improved Two Weapon Fighting at 8th level as a free bonus feat, and Greater Two Weapon Fighting at 16th level as a free bonus feat. They must still meet the prerequisites of the feats to benefit from them.
Elven Blade Master (Su)
At 20th level, you gain a +2 circumstance bonus to all attacks made when wielding two light bladed weapons. This ability replaces the true magus ability of the magus class.
Magus Arcana:
Dual Bladed (Su)
Benefit: When wielding 2 light bladed weapons, she may spend a single point from her arcane pool to use Dexterity instead of Strength in determining damage with her primary hand. This effect lasts for one minute. At 7th level, she may add her dexterity bonus to her damage rolls for both weapons rather than just the primary weapon during this effect, this raises the cost to two points from her arcane pool..
Overall, I think it's a decently balanced Archetype, if even slightly underpowered, but instead of your Diminished Spellcasting, I'd recommend the following:
Diminished Spellcasting
Due to their intense martial training, an elven blade master's magic focuses inward rather than towards others. Whenever an elven blade master casts a spell which includes any targets other than themselves, they must make a concentration check as if casting defensively (DC 15 + the level of the spell cast) or lose the spell.
This covers corner cases such as two-weapon fighting with a double weapon to leave one hand free for spellcasting, using still spell to avoid needing a hand free for somatic components, or the like. Even stuff like party buffing with Haste becomes a calculated risk.
With the Two Weapon Fighting and Bonus feats, I don't like the restriction of 'They must still meet the prerequisites of the feats to benefit from them.' I would suggest just giving it to them at the selected levels.
Also, Two Bladed Defense doesn't seem to make sense to me. You specifically call out the bonus to AC as a 'Shield bonus' (which I'm guessing you took from the action Two-Weapon Defense feat) and then say that the bonus increases later. Then further in you say it doesn't stack with armor because it's an enhancement bonus. Shields and Armor are separate so I'm curious why this shield bonus should overlap or negate (if the armor bonus is lower) armor bonus.
So following this correctly, the SHIELD bonus at level 17 would equal +4. Even adding their weapon's enhancement bonus as an enhancement bonus to their Shield AC would not affect their Armor in any way.
In addition, when enhancing their shield AC by their weapon enhancement, how long does the effect last?
Does the bonus from Two Bladed Defense stack with Two-Weapon Defense?
If some other class, spell, ability, item, whatever, is dependent on Two-Weapon Defense, does Two Bladed Defense count as that feat?
Lastly, the Arcane Pool change seems silly. If he has to spend two points to buff both weapons, that seems to essentially cut his full level pool in half. You could easily leave it as half his level, but 1 point spent buffs both.