CatintheHeat: You are right in a way. But what is the sense in playing any video game, to have fun. The addiction in well built ARPG's is goal oriented in gaining complete sets of gear, or beating a boss at the highest level. But you are correct in that they can be time sinks. But again all video are time sinks unless you are playing them as a simulation to increase your skills in real life. Mostly video games have become a cheap form of entertainment. Spending $5 on a game I can play for weeks before moving on is sure a lot cheaper than going out to theater to see a movie, even one time.
You are right. Maybe I didn't have the perseverance to take these games that far (beating the boss on the highest level). I don't play games to increase real life skills. But I tend to prefer games that leave me satisfied in a way that a good book does. And this just didn't happen with ARPGs so far.
I play a whole range of games, mostly RPG nowaday, but also arcade, shooters, adventures, racing. In the past simulations and TBS, but I don't have the time to learn these complex beasts anymore. I guess I draw my satisfaction from either a good story or "having to do things/perform well" to beat the game. In case of ARPGs I can't feel neither - story is mostly just an excuse to kill things and the killing itself is done in a very simple way that doesn't require a lot of skill or strategy. Might be different on the levels you play. In the case of Torchlight I bought tons of the "treasure maps". Even if they could be difficult they just wouldn't give me the same feeling like beating a level of, say, Final Doom in Ultra Violence mode. And after this the regular "story" maps became ridiculously easy.