You know, I see people always wish that DMD was harder, I don't think Dante Must Die needs to be changed at all. The mods and stuff I play with that should jsut be optional stuff for people to have fun with. The game is balanced really well as it is, making it too defense focused would ruin the overall game design, which is about getting better at doing combos and increasing your overall score.
The only thing I'd suggest is the 20% Turbo boost (options for 25%/30% as well) with the default difficulty set up, and some modification on how weapons affect colored enemies (ie Only proper weapons damage them at 100%, while all others damage them at 50% and do not cause them to stagger, maybe they even make them devil trigger faster). I'd also debuff some of the damage boosts on Dante Must Die to 75% of their normal versions. Other then that, the game is fine as it is. I notice a lot that people that request higher difficulties don't themselves play them, I don't really get this honestly. I like playing games on a higher level, and I don't want the game to be frustratingly hard. I like the balance between me just trying to get better and the game giving me some good strategic encounters. Hell, if you play DmC with the idea in mind that you shouldn't ever take damage, then its already as hard as it needs to be for 99% of players.
Honestly, if people saw how difficult fighting that many dreamrunners is, they'd be like fux this. It is indeed cool to try out, so like I said, custom wave options and **** like that would be awesome to see coded into the main game. So you could just set up crazy waves and send them to friends to try out.