Proper working QoS is only possible on the outgoing interface of a router or host, where the bottleneck begins. Everything else is a hickup and not subject to work as expected or has a successful result.
-------------->-------
Queue 1 \
--->--- ---->--------->--------->---------------
Big pipe Queue 2 Queue 1 / Queue 2 / Queue 3 Thin Pipe
--->---- ---->--------->--------->---------------
Queue 3 /
-------------->------- |