I think the biggest problem is that to get good random loot 90% of the time there is no 3rd slot. Once you get the 3rd slot you have to have the dice add up to get a useful triple combination.
Looking at 2 slot CC items I would have no problem with them. I can get the same thing spending the time on the auction house over a period of days (depending on how many people are playing).
Crafting specific 3 slot items which have 2 augment slots makes astronomically rare drops that the RNG has never even created with people running loot gems during bonus events....
Solution, add 2 new 3rd slot recipes:
Epic Mark of House Cannith Slot: Adds the 3rd slot to an item that has been made level 21-30 (rare trade-able drop in level 21-30 chests)
Legendary Mark of House Cannith Slot: Adds the 3rd slot to an item that has been made level 31-34 (rare trade-able drop in level 31-40 chests)
Mark of House Cannith (purchased by from favor store or found): Adds the 3rd slot to an item that has been made level 1-20
People can still make level 1-20 twink items easily like the old system but to make level 21+ ultra rare items it will be significantly harder....
As it is, I will be a level 250 crafter in the new system and should be able to make some ultra BS equipment (more after a 15 minute grind with an xp pot). I think it will kill the end game 36-40 chest loot desirability unless we make that 3rd effect harder to get.