Yeah I started using the promy areas to work on my magian wep skill trials (use shining blade on an experience yielding mob 200,000 times yada yada yada) Its nice because nearly every mob even on the 4th floor is TW but there are Idle Wanderers (and a couple other mobs) which are EP and seem to serve no other purpose in the game (to ensure there is a very slight difficulty to Promy missions?? They are extremely easy to avoid so IDK.) But anyway its easy to store tp on the TW and WS on the EP, and I did notice that I was receiving skillups 300+ (Marksmanship 320+... almost capped lol)
On a side note the 3 items you can receive for trading in the recollections dropped from the NMs in Promy-Vahzl (which are popped with the drops from the NMs on the 3rd floor of each of the other 3 zones) are extremely easy to obtain now. I was able to get all 3 pops and all 3 maps and 3/3 on drops from the NMs in abot 3 hrs combined total time. (So either I was extremely lucky - which never is the case for me - or they changed the drop rate) Man I get side-tracked easily =P
So anyway, yeah Promy's are a great place to skillup.
Also I don't know if it still works or not but another place I used to skill up when ToAU first came out was the T1 or T2 Lebros Cavern assault mission where you gotta knock down all the walls (can't remember the name, sorry.) I remember skilling up both magic and combat sills as RDM. And although I understood the high defense, I was always curious how a wall could have high evasion, LOL)