Matthew,
Is my only option to have all the code declaring the class in the file that uses it?
Definitely not, XOTcl object declarations (as Tcl procs) go into tcl/*-procs.tcl files and are provided to all request-serving threads ("connection threads") through the AOLserver blueprinting mechanism. As for the development cycle, stage your code in www/* scripts, once consolidated, move them to *-procs.tcl to have them served for a wider scope.
Btw., may I give you an advise. Try to manage your code in a publicly browsable location, so when posting questions, you may refer to your package structure/ code. this opens many opportunities to help out more effectively.