So this is for a fighter type character with shields, but with a sprinkle of magic? That feels a bit vague for a class, it might be better to pick more of a focus beyond "defense".
You really want an ability every level. Spellcasters get spells each level...why don't martials? I know the publishers do it...but it is still wrong. You also want abilities to scale up
1st level is shield ally...I think this should be shield focus. Shield Ally would work better worded like "You may assign some or all of your armor class points to one ally inside your reach as an immediate action". I would just leave it up to your full AC, but you could limit it to half if you feel that is needed.
2nd level-Provoke? Feels like an odd magic ability that can be used at will. Maybe, for the low level ability just make this like the Taunt feat: (EX) will save vs Intimidation skill, If they fail, they must use their next action to move closer and attack you.
3rd level Shield Focus is fine, but I'd put it at 1st.
4th level is Rooks Defense, another SU and teleport? Maybe just a bonus to move, not teleport.
5th level is a dead spot. I'd plug in a shield feat here. Shield Specialization works.
6th level is the dual shield feat, and this might be a bit early. Maybe another feat? Or some shield stuff from the knight class?
7th level dead again. This could be make focus +2 and maybe Bulwark of Defense (Ex): When you reach 7th level, an opponent that begins its turn in your threatened area treats all the squares that you threaten as difficult terrain. Your strict vigilance and active defensive maneuvers force your opponents to move with care. Or the spell Shield Other.
8th level Rook is fine here, but maybe make it once a day per Chr bonus.
9th level Provoke....effecting immune creatures is a bad idea. And it's not like "provoke" is a huge part of the class. But with lower level mundane, put the SP magic one here.
10th level is stout guardian? This does not really fit. A good shield user(should) is not going to get hit all that much. Maybe Wrathful Healing: Whatever damage is done, you heal half that amount. SP once a day.
11th level provoking aura? Would you even want this? Though maybe missle attraction?
12th dual tower shield is fine
13 th dead level Fortification? Ghost Touch?
14th sheilding aura, maybe just more a bit like advanced shield other?
15th Some abjuration like anti magic or wall of force fits here
16th-20th are just about empty
Once you get past 12th level or so, you really want to put the magic abilities here. There are a TON of them to add. Put some damage resistance or energy absorption(and space them out every three levels).
Animate shields
Tower shield: Warriors Tower (like mages mansion)
Mettle: You can resist magical and unusual attacks with great willpower or fortitude. If you make a successful Will or Fortitude save against an attack that normally would have a lesser effect on a successful save (such as any spell with a saving throw entry of Will half or Fortitude partial), you instead completely negate the effect. An unconscious or sleeping character does not gain the benefit of mettle. Really fits this class
And...well, the Captain America throwing shields.....