every character illustrated by suzuhira hiro looks the same....

Uh... what? The same can be said of more or less any artist. Take a look at Nishimata Aoi's works for a good example.

Since I become very familiar with Suzuhira and Nishimata's style. All girls with blue hair illustrated by them remind me of nerine in SHUFFLE. Now I wish I could distinguish those characters.

Let's just say it is a good way to distinguish the artist from the others...usually. As for the characters...give them different hair styles along with accessories and such so it's better to tell them apart from that artist's other characters.....heh heh...it~ can be hard at times though.