I'm just before chapter 18 in Engage and I'm really enjoying it now. I settled into it once I progressed past the first 'act', where you learn the mechanics and systems and are then pushed to exploit them. I can see the game having a lot of replayability - the flow of it is a lot smoother than 3H without the tedious monastery sections - and they throw an absolute boatload of characters at you. The ring system is also really interesting once you get to grips with it and offers a ton of experimentation. I did cave on the DLC and both of them are really fun to play with; my Anna snagged the Tiki ring and has snowballed into a monster, surprisingly.
I'm playing Hard/Classic and I'd say the difficulty is a little under where I'd like, where Engaging with the Emblem Rings is superfluous for actually clearing through main chapters, though the paralogues have offered a good challenge. I'm really looking forward to going back through on Maddening and eating my words!