I too could not stand Diabolik Lovers but the female lead was not my biggest peeve, virtually everyone else was.

When it comes to reverse harem the first thing that comes to mind is the Uta no Prince-Sama franchise. It's about a bunch of prospective idols crushing on the girl who happens to be their composer. It is full of cheesy moments and expect each boy to break into song almost at random so it is not something to take at all seriously. Still, it's enjoyable for what it is and there are enough different boys to appeal to virtually all demographics. As for the girl, she is indeed a bit bland as tends to be case in this kind of anime but way better than the usual fare. There is some conflict surrounding her vocation as a composer so her character is more developed than one might expect even if it is hardly all that deep.

Starmyu may fit the bill as well. More idols at school, more bursting into song complete with spliced-in videoclips that come out of nowhere. No girls and no actual romance either but for all practical purposes it is about as harem-ish as it gets. The MC goes around 'capturing' each boy to make them commit to their unit and it plays off as borderline romantic to the point it has to be intentional.

As for actual male on male harem, there is Marginal Prince. Also includes every single boy bursting into song at least once per episode but in an even more awkward and less understandable way. Production values are also exceedingly poor, it's a bit the Gakuen Heaven of the poor.

None of my favorite BL mangaka does harem but I can recall Honey Boys Spiral from Minami Haruka. I am not at all a fan of hers and this particular title is not my cup of tea, at all, but it does include an all male cast all lusting for the main boy. Just be prepared for a lot of sexual content and weird anatomy.