" I just wish it was like IN where you could have cav only stacks, they were awesome fun "
This is my case I play IN, this is important? The combine bonus work in In Nomine?
The other cavalry advantage that IN has which is gone in DW is that cavalry is faster than other unit types so an all-cavalry stack could move a lot faster than a mixed stack.You can still have pure cav stacks, you just miss out on the extra Military Tactics. Charge cavalry stacks still rule the early game though.
(And in 5.2 artillery no longer slows a stack down either; all units have the same speed.)