Antes me pasaba lo mismo que a ti, la solución que yo encontre fue crear un script para que me los registre, aqui te lo pongo
Código vb:
Ver original@ECHO OFF
sn -Vr DevExpress.Data.v7.2.dll
gacutil /i DevExpress.Data.v7.2.dll
sn -Vr DevExpress.Web.ASPxDataControls.v7.2.dll
gacutil /i DevExpress.Web.ASPxDataControls.v7.2.dll
sn -Vr DevExpress.Web.v7.2.dll
gacutil /i DevExpress.Web.v7.2.dll
COPY DevExpress.Data.v7.2.dll "C:\Program Files\Developer Express .NET v7.2\Sources\DevExpress.DLL\"
COPY DevExpress.Web.ASPxDataControls.v7.2.dll "C:\Program Files\Developer Express .NET v7.2\Sources\DevExpress.DLL\"
COPY DevExpress.Web.v7.2.dll "C:\Program Files\Developer Express .NET v7.2\Sources\DevExpress.DLL\"
Saludos