If you're a person who gets stuck on aesthetics, you're going to die here. Just about every anime series has fanservice; this was the Divergence Eve way of doing it (large breasts, that is). But, as with a bunch of other series, including Gilgamesh, once you get used to the character designs, you can focus on the story.
Divergence Eve season 1 was really... it had a bad start. Episode 1 is actually episode 12 (I recommend watching it as episode 1 regardless and not as episode 12), the CG looked like crap, and then there was the breast factor. For the first three or so episodes, it seemed like pure fanservice. I'd say that if by episode six or seven you're not clawing for the next episode, then watch up to episode eight and then decide not to watch it. The storyline is extremely dark, and it's quite an interesting contrast they build here by having characters fit for a sex comedy harem series inserted into one of the darker, twisted series you can find.
As for whether you should watch Season 1 before Season 2, that's a yes. You'll be lost in Misaki Chronicles for a bit, and while you may be able to catch on, a lot of the effect will be lost on you. That aside, it'll make viewing season 1 more painful, unless you buy the DVDs and watch those, simply because technology has progressed between the time both series were made, and not only do our fansubs look better, but the work on season 2 looks better as well (huge improvement to the CG and animation).
Divergence Eve was the series that drew me to AnimeForever