Hi Grame,
Improve performance - by designing InfoCube dimensions correctly in #SAP #BW
As mentioned in the above blog:
"Use as many dimensions as necessary but it's more important to minimize dimension size rather than the number of dimensions."
You can create many dimensions as required but keep the size of the dimension low.
"Within the dimension only characteristics that have a 1:n relation should be added, Within a dimension there shouldn't be n:m relations."
As per the above statement and your knowledge which you got by" reading couple of Articles before working on this development" 
Please decide to create the dimensions and place the characteristics.
And on checking High Cardinality, just for info
High Cardinality Purpose: If data volume stored in a table is very huge, it's difficult to retrieve particular record or sets of records. For fast retrieval purpose system creates Indexes on various columns, by default SAP BW creates 'Bitmap' index on each dimension.
If dimension doesn't contains large number of distinct values 'Bit Map Indexes' are fine, but in case distinct values are high and the dimension table is at least 20% of the size of the fact table, SAP recommends checking the 'High Cardinality' check box to create 'B-Tree' indexes. When compared to Bitmap indexes B-Tree indexes data retrial is fast, this is recommended on Oracle Data base.
Regards
Sunil