this is true. in most other MMOs i've played, there are perhaps as many as 15 different "spells", if that, which a player can use. in DDO, even the sorcerer gets 36.
and furthermore, the spells in most other MMOs tend to be pretty much the same kind of thing. you have roots and mezzes and such, and maybe a couple of other status effects, and generally the spells apply from the same limited selection. and even then, you likely only get that many different spells if you don't specialise... in fact, that's probably too many. i've played other MMOs and never felt like i needed more than 1 hotbar, with maybe an overflow if that. on DDO, the first thing i do with a character is start setting up about 8 hotbars. and that's for my melees, who don't have 30+ spells to keep track of.