First - awesome job on all these builds - I just stumbled on this thread and wish I would have had it six months ago!
Second - apologies if someone already brought this up, but I'm not scanning through 20+ pages of replies (and the "search this thread" option seems to be fubar'd). I think splashing rogue has more advantage than just UMD; you can take Rogue Haste Boost and have 15% bonus to attack speed 5x per rest. It will work with either ranged or melee over all 20 levels (assuming you take rogue first, which I would to dump lots of points into UMD), which IMHO is a great trade-off for having 25% ranged once you get to level 20.
Add to that sneak attack bonuses, plus decent trap-monkey abilities with the right gear.