timmmay:

 

If the air is all recirculating via a ducted heat pump it probably doesn't matter much which rooms it goes into directly, it will make its way around. 54% humidity is fine. My office where I am right now is 58% and it feels fine.

 

It does matter to a degree.

If the fresh air goes into the room closest to where the heatpump pickup is then its not to bad (mitsi diagram has it going direct into the heatpump). But if its another room its pretty poor as its no longer fresh air. eg if goes into the kitchen then goes to the heat pump pick up, its also going to take with it all the cooking smells, similar effect if its near the bathroom, bedrooms etc.

Also keep in mind the fresh air going in wants to go directly to where the air is going out (high pressure to low pressure). If those points are near each other a lot of the fresh air will simply bypass the house and go outside. In this case, a proportion of the fresh air will be doing that as the exhaust is tied into the heatpump pickup. Its going to the 2 rooms then to the heatpump inlet which is also the ventilation exhaust, so part of the fresh air flow will simply be exhausted outside. Not horrific but could be better. No doubt why mitsi diagram has the ventilation with separate exhaust.