Good news! Titan Quest has just gone on sale, so if you're interested, this is a good time to pick it up.
I made zero mention of Ember. Fantastic game, but not anything like Titan quest or Diablo. It's a baldurs gate style classic rpg, not an arpg dungeon crawler. Def reccomend Ember overall though, it's really great.
You can try Dungeon Hunter 5. The game is actually closest to Diable in the Ipad but this resembles Blizzard's masterpiece.
There is nothing like it. They are all arena minute based. The closest is IRE in gore/dark setting, but even this is gated in small arena stages. The rest are bloodless, goreless, flashy arena stages full of pandas and boobs, and require serious amounts of $$, enough to buy two AAA console titles at full price(or more).
If they just took DH5, made it like Titan quest, added multiplayer and a few other modes it would be a perfect mobile arpg.