I just did a solo Archer playthrough and I took Guerilla. 25% is worth it.
However I was going to be sneaking anyway as with one player you have to. For longer (tougher) fights it gets boring though. Snipe has such a long cooldown you might be better off with Warlord.
Most likely I did more damage overall with 2nd turn rage + marksmans fang than sneak + snipe.
I do wish enemies would look around a bit more. Even the worm at the end doesn't seem to bother any more. There is no fight in this game that do don't win with a solo Archer (as long as you don't die in the first round). 24 Initiative, sneak, you win.
