Because Forsaken can walk right up to unsuspecting Aes Sedai and
compel the tar out of them, there has been absolutely no reason for
the Forsaken not to have the White Tower, or in fact every other
royal House or other contender, completely under their thumbs from
long before the Dragon reappeared.
Except thst they've only been out of SG for a few years, if that. And
what have they done in that time? Be'lal became a High Lord of Tear,
Rahvin took control of Queen Morgase and Andor, Sammael ruled Illian,
Messana integrated herself into the White Tower, and Semirhage has
control over one of the royal Seanchen. What more would you have them
do?
And if what we've seen from Verin, which I interpreted to be
basically a post-compulsion suggestion, there's also no reason for
any of Our Heroes to still be alive - capture some anonymous maid, or
spear sister, compel her to poison or shiv the Dragon, or whatever,
and there we go.
As for killing Rand: Aginor and Balthamel fought him outright, Ishamael
tries to subvert him then fights him outright, Lanfear tries to subvert
him, and he has about forty darkfriends attempt to kill him, Mat, and
Perrin in the first three books. Apparently he's good at what he does
and not-surprisingly lucky.
The only possible justification for this storyline is either that
Rand has to make some kind of a decision in favor of the Dark One,
and that killing him won't on its own earn the Dark One a victory,
or just the usual bungling ineptitude of the Forsaken.
Or Rand kicks ass. Everyone knows Rand is to be the end-all-be-all of
kick-assers, so they try and get him on their side (during other
turnings, Rand did join the Dark One), so they try that first. Then
after a lot of failed assination attempts, the DO said no one is to kill
him.