Ok cool
But seriously, you are making a big deal out of very little. I personally got through that specific puzzle first try (because I'm not bad I guess) and like you said, you can just go back into town and sleep if you run out of mana. Also, while there is difficulty, its really not game breaking (and I play on normal). Its a healthy challenge (although it can feel slightly unbalanced at times).
HOWEVER, Ni no Kuni is far from the amazing game it was painted as. It does have a lot of flaws such as the incredibly stupid friendly AI and many other things that just aren't done as well as I had hoped. If you aren't charmed by the presentation, stay away from this game. There are other JRPGs that do things much better but the thing that makes this game special is the presentation and that is what keeps me playing.
Sorry that you didn't like the game but swearing off JRPGs is hilariously petty :P Try looking at some DS/3DS games or play Xenoblade...







