3D assets don't have such a big issue, as animations and so on can be easily reworked (for instance). Sprites are very time consuming to make, especially for modern resolution demands, and they're very hard to modify too. Regarding D6: NIS' decision to build a new (presumably) engine that uses 3D models was fundamentally the right one.

Many will say D5's story isn't the best in the series but honestly, most of us aren't playing for the story anyway. It's just brimming things to do, and ways to do it. Having auto-battle available for key stages tied to progression feels cheap and detracts from the story somewhat.D5 is the gold standard in terms of content. I think its use should have been limited to grinding in the item world and other nonessential stages. The only downside is that it can sometimes feel as though battles aren’t worth playing manually, as a well thought out auto-battle strategy is often the fastest way to clear a stage. Having this level of control makes auto battling surprisingly skill-based, as you have to consider how the AI can get the best use out of each unit.

For example, you could set a support unit like the Clergy to check for their allies’ health levels, heal them if they’re low, check their own health, heal themselves if they’re low, or attack an enemy if none of those statements are true.

This allows you to give specific units more defined instructions as to how they should act during auto battles. Rather than just having generic presets to instruct the AI with, the game implements a flow chart mechanic. It’s also one of the best implemented auto battlers I’ve seen in any JRPG.

Instaling Disgaea 6 Complete