I roll this concept with a more balanced approach - a Rog13/Monk6/Ranger1 split. I lack the Autovorpal and 3d6 Sneak but with slightly higher HP, always-on 25% incorporeality and very fast movement speed (Ranger Sprint boost/Monk6) it's very, very durable/quick for a Rogue. Plus you get some more Monk goodies like tier 2 stances/strikes and an FE as well as easy cure wand use at lower levels.

I'd really like to try out your split but it seems to me that 19rog/mnk1 works best when you have access to great equipment to overcome the survivability weaknesses and you want to go all out on DPS. There is nothing more enjoying for me in this game than seeing a Lotus hammering a boss with hasteboost IV.