That's fair, but i think its more to do with mortal blow being a great ability and less with guerilla being viable, and all of this assumes you start the fight while sneaking. Besides, if you're going to use mortal blow constantly, I'd argue warlord is a much better talent and you only need 1 point in warfare, or you could grab pawn/speedcreeper for extra mobility if you're gonna be sneaking alot. Infact there are so many other talents that are better for rogue (Backstabber, Leech, Hothead,etc...) that grabing guerilla is more of a joke than anything else.
