^To your last point--first, as far as we know, Koval had overseen a Tal Shiar plot to assasinate the deputy chief of SI. So, if we're going to compare extent of manpulation...
(Interestingly enough--the cover was the admiral suddenly came down with a disease...much like what happened with the Praetor. So...surely the Shiar would recognize its own methods?)
Second--again, the manipulation of 31 by the Tal Shiar occured before
it was revealed that Koval was a mole--some years
before. It's likely--in fact, probable
, that Koval was not a mole as of Rogue
My personal theory (which I actually borrowed from another fanfc writer) is that, following this, Sloan effectively blackmailed Koval into becoming a mole via the threat of expoing Koval's involment in the admiral's death. A bit of "payback" for Rogue
, if you will. (For a dramatization of this, I recommend my tale "Of Mastery And Fate", which you can find in the Fanfic forum.)
But back to a previous point--the virus. Again...how could the Tal Shiar allow foreigners to have the opportunity to come into such contact with the Praetor so as to have her infected? Has it really become so incompetent, over the years since Koval's assasination (an event that is, in itself, a bit astonishing, on that account)?
BTW...I find it amusing that, for all the Tzenkethi's best-laid plans, the end result was a level-headed Praetor that is, because of such, in a much better position to bring the Romulans into a position of greater influence in the Pact. So, then...the plan backfired!