Honestly I'm not even sure D2 satisfied me on that front either. Usually with Disgaea-type titles I'll wind up having done a reincarnation or two, leveled at least one omni-stat item, grinded the heck out of Hospital, ect.
D2? None of that. Due to the promotion system I pretty much ended the game with the same party of 8 I used from square one (sans a Chapter 7+ swap out of Sicily; trying to make her use a gun was a horrid idea). No Item Level grind, no reincarnation swaps, and the Hospital actually remained largely ungrinded. The 'strongest' Omni-stat item I ended with was a Sophia's Mirror. :-\
Maybe it's because I actually used 3 MCs this go (Laharl, Flonne, Fuka-DLC) which are typically over-powered in Disgaea games, but honestly the make-your-own units often felt just as strong, if not stronger.
Heck if anything, in hindsight, I think the Monsters actually now break the difficulty of the game. There were far too many maps where I just had a Mage hop on a Ghost and, as I call it, Orbitally Nuke everything in sight using Dimension Eater X with a Fight Mistress/Moth cleaning up everything else (despite her low SP count). Those skills are easily 2-3 times more powerful than anything anyone else can throw out and definitely turn tables in an instant.