On the Iceheart topic: given the framing and whatnot, I really can only see it as Iceheart erecting the barrier, not bringing it down. There's just no visible effect at all to start with, and it's after the flash of light that there's an obvious wavy barrier.
What I suspect is going on is this:
Iceheart's mission, assuming she is telling the truth, is reconciliation between Man and Dragon. She wants conflict to end, not for Ishgard to get blasted to powder. To date she's mostly tried to hinder Ishgard's ability to fight, but once the Dravanians begin their full-blown intended-as-the-killing-blow assault on Ishgard, the woman who was once Ysayle the Ishgardian realizes she has to intervene on Ishgard's behalf to avoid full blown genocide. So she helps erect the barrier to try and prevent Ishgard from getting mobbed from all sides, possibly necessitating the bridge assault (to break through the barrier at a fixed point).
This will also possibly serve as a moment of revelation for Iceheart, as she realizes her focus has been too narrow - there are just as many Dravanians willing to see the war to a terrible conclusion as there are Ishgardians. Many on both sides believe the war can only end in full-on genocide, and she realizes she must stop them both - likely recruiting us to help stop the war in the process.
I'm more looking forward to the Keeper of the Lake dungeon, personally. I want to know exactly what it is Iceheart learned, and just what Midgardsormr knows about Dravanian history.
And, of course, how it all ties into the Allagan-Meracydian conflict revealed in the Coils of Bahamut and Crystal Tower storylines. The current storyline has stopped about two steps short of outright saying the Dravanians are the descendants of the enslaved Meracydians who were stranded in Eorzea following the fall of Allag, and I'd like to learn exactly what happened with them after Allag's fall and what Ishgard did to start the conflict - especially as I suspect it'll appear small and petty to most people, but is something the once-Meracydians took as a prelude to enslavement and drove them to a war of extermination for their "freedom".
But this might also be off-base! I'm eager to see how much of it is right.