You know me and what I like in games (action, depth, challenge, etc.). and this system hooked me. I literally couldn't put it down trying to unlock new stuff and make my party stronger to fight more powerful monsters.
Rather than try and convince you etc. just do me a solid and read this review (this is a site I frequent for RPG news info):
http://www.rpgfan.com/reviews/manakhemia/index.html
Regarding the time bit, yeah trust me I feel you. I loved Persona 5, but the 100 hour journey was rough on me. Really rough. I basically didn't play any MMO/games during those 2 months and played the game non-stop. Persona is another one of those games (like Mana Khemia) where the more you invest in the side stuff, the more exciting the main bit is (story/combat).
Also now that I can add you to f list I have to shoot you one! we can queue up for Rabanastre or something!