Alternate Strategy for Thieves:
3 thieves use two each.
Assume Lyre Spawns in Dinining Room.
1st thief just bolts for the dinning room and grabs the lyre (2X speed, 2X invis, 2X catwalk). Assume he is killed. He now has 500 loot and it as exit, he gives his loadout to the second thief who repeats the exact same proceedure. Then the 3rd theif does the same thing. When the third thief dies he spawns in the exit and the three have a total of 1500 loot AND are in the exit already.
There is no way to defend against that because the strategy is FOR THE THIEF TO DIE which is exactly what the guards will try to effect, thereby loosing. The thieves have a total of 12 invis, 12 speed, 12 catwalk to get three thieves to one known location. All they have to do is pick the item up and die and this doesn't even begin to deal with the unfortunate possibility they get away with the lyre.