@Clemens
To me a good turn-based game is NOT based on skill or learning the mechanics. "Skill" in that respect would only mean that you know how to beat the numbers. It's not about being fast or having good reflexes like in first person shooters. There is no skill in games like D:OS. To be able to react with what you have to a challenge ahead of you isn't based on skill but on basic intelligence.
As I said in my post before, I think that the game should offer a lot more randomness. A game like D:OS which is based mostly on number games and simple causal combat mechanism (actio->reacio) is somehow "dead" to me. You beat every enemy by the same patterns or different set of patterns based on their resistencies and stuff.
I think a good game with some "challenge" here should mean that you have to die in hard fights. Maybe two times, maybe ten times, maybe you make it in the first attempt. Since many stuff is based on random principle you can never know how it plays out in the end. That's the basic principle of many board games as well, at least the entertaining ones. They combine tactics and strategy with luck. A game which is only based on one of them is either too chaotic or too boring and expectable...
As you mentioned in a previous reply, the argument is largely philosophical, but I could not disagree more with this.
Luck based mechanics that determine whether or not you win or lose fights are the most frustrating and unrewarding things you could put into any type of game.
There is nothing worse than going into a fight 5 times and die each time all while knowing you made all the correct decisions but just got really unlucky. Then, when you finally win the fight, there is no sense of satisfaction since you know that you would have probably lost if your 5% chance to insta-kill spell had not succeeded.
I do agree that a game with challenge should mean that you die in some fights, but those deaths should not have anything to do with luck. Whenever you go into a fight, you should be able to win 100% of the time if you make the right decisions, and all the information to form those decisions (enemy abilities, resistances, etc.) should be handed to you upfront, not through several deaths of collecting information.
I would much rather have games challenge me to think through my actions before doing them than challenge me to beat my head against a wall multiple times until I am lucky enough for it to give way.