I have only seen the first season. I went in knowing as much about the series as you, being aware that it is a popular franchise but knowing nothing else.
I had my expectations pretty low when I started the first episode. The turning point for me was at the end of the episode when one of the main characters says "Baka, baka" after something completely stupid and ridiculous happens, that's when my brain went "Oh it is OK to laugh at this, they are just being silly in this show."
Then the rest of the season was a goofy ride full of anime harem shenanigans. On a technical level, DAL isn't really special, though the characters, character designs, absurdity of the setting and the OVA punch above their weight.
I really liked DRG. Have maxed out all the classes and enjoy carrying people through Haz5 and EDD. However, DRG:Survivor from the very first announcement just seemed like nothing more than a cash grab to me and made me uninterested in it.