With regards to replying to emails, are my expectations too high from Group leaders? I am currently looking for Post-doctoral positions after finishing my PhD. I have recently visited a potential lab for a lab visit. It has already been two weeks since I came back from there. Since then, I have not received any communication negative or positive. I also reached out to the Group leader with no response. 

I am in an extremely specialised and competitive sub-field, so I cannot keep on sending out applications, because most of them come back positive with a pre-emptive interview call. Later on, I might have to send decline mails for any or all positions that are offered. And, I know that even as a Group leader it doesn't feel nice to get snubbed.

Right now, I feel a bit angry. The response from the Group Leader was extremely prompt while setting up the visit. Now, I do not get any response. And, I have no indication of when one might be forthcoming. So here is my question. 

If I as a potential Post-doctoral fellow am expected to send out decline emails for positions that are offered, is it too much for me to ask the same of a Group Leader? Mind you, I am not expecting them to reply to the first introductory email. But, if I have made it to the last screening round, shouldn't I expect a response, be it positive or negative?
As I have come to do again and again lately, I completely agree with @Buffy. You need to calm down and take it easy. 

You have no idea what might be the reason for them delaying a response, it could due to:


delays with the paperwork to the rest of the faculty, 
delays with interview all candidates, 
delays due to other urgent matters such as grant/paper deadlines, 
or simply some sort of personal emergency


2 weeks is not an insultingly long time, so you have no basis on which you can demand an answer. These are busy people we are talking about. 

On a different note, it wouldn't prevent me from applying to somewhere else. Everyone who has ever applied to a position, or hired a person, knows the dynamics of this "game". Apply to other places if the wait stresses you, and you can always say that you had a more favorable position when you turn down a position. As long as you haven't played foul (i.e. lying, withholding important information etc) nobody should get upset.