WIS dependence - its hard to keep 3 stats high. Widening the Aegis burst is also cool, but it doesn't become truly incredible until Epic tier when you get Total Aegis - how often are there going to be no two enemies you can't get in a burst 2? If you're following my advice, you can start nailing 3 in Paragon tier (because of Shielding Fire!).
First of all, I'd argue that you don't need a fantastic Wisdom to make this Paragon Path work well.
Most of the powers aren't going to have significant enough effects to warrant a big increase in Wisdom, and the Aegis Insight (or Arcane Tanglestep) benefits tremendously from even a small increase in Wisdom.
Increasing the size of the Aegis burst, even by one, is a big improvement.
In your pbp, Red Hand of Doom, think about how many times the wizard has been at least 3 squares away from the fighter (most of the match).
The Swordmage's Aegis doesn't try to keep enemies near him, but tries to keep him near the enemies. Increasing the size of it lets him be, arguably, wherever he wants to be.
It's especially useful if the group that the party is fighting doesn't start together. It means that the swordmage can tag the foes that much more quickly.
Teleportation action is nice. Four Corners Attack is nice because if you attack vs Will you can Daze, and Swordmage attacks vs Will are rare. I'm not sure I like Arcane Tanglestep - I mean, if I teleport myself out of combat, then I'm kinda out of combat for a round (unless I charge back in and then I'm not using powers...). If I teleport myself into or around the main melee then I'm flanked and might have locked myself in to a bad situation? I'm sure its not always that rough a decision, but why subject yourself to that kind of choice, y'know? And while Heritage of Blades is nice, there are other good stances coming up (Shackled Warding, Quicksilver Blade).
Teleportation Action is
really nice. The swordmage, despite claiming to be a defender, has a surprising mobility aspect to him.
I haven't played one personally, but it seems to me like this "defender" doesn't stand still and keep enemies nearby, so much as he teleports around and gets in the way of all of the enemies. Teleportation Action is like a free setup movement.
Based on my interpretation of the swordmage's purpose, Arcane Tanglestep looks like a great power that gets exponentially better on two conditions:
1) There is another defender in the party (fairly likely)
2) There are map hazards
With Arcane Tanglestep, you take a nuisance foe and stick him next to a fighter or on the other side of a chasm.
Then, when another enemy attacks your allies, you can just teleport back into the thick of it. It seems like a step up from the traditional Aegis effects.
I don't really know what to say about Heritage of Blades. It looks like free damage each turn, and when you consider that hitting something is never really easy, free damage really adds up.
I like it, I just don't feel like I can recommend it over Coronal Guard.
Coronal Guard is
good, but I think that Wandering Swordmage is pretty much the equivalent for Aegis of Assault Swordmages.