Not entirely true friend. Rand in fact attempted to blow up a battlefront, and help out Rand, but they had channelers going straight for him whenever they saw him. Also, with demandred in a full circle, it's doubtful Rand would attack - thats why only the non-channelers had any luck with kicking his butt. Logain had a serious issue. 

With no Shai'tan, the DR would have gone all out, use Callandor, game over.  The Power, skill and abilities of the DR is unmatched, expect in TAR.  The Forsaken are hardly a match for a farmboy, let alone LTT, forget about Rand Sedai. 

 

Callandor, it has no buffer, at one point the amount of saidin wielded was greater than at the Cleansing (according to Logain's PoV).  He would smash Demandred and his little sa'angreal, full cirlce and his armies, main threat over. 

Doesn't having no buffer imply you can do this only once?

 

I liked the her in this book if simply because I predicted an Eldrene-style ending for Egwene.

Some character just HAD to die that way.

 

Could somebody explain to me how she knew the light would be the signal to break the seals?

From one of the prophecies, though not directly. An Aes Sedai who had been studying them had written a note in the margin. I think it went along the lines of "Wait for the light".

I took this to mean that they had to wait until just after the eclipse that was foretold. Obviously I was wrong though.

"Wait upon the light". It's somewhere in the early published chapters.