Normally yes, but with difficulty that high some of my rigs won't find a share for lets say an hour.  During that hour my hash rate is considered zero by nicehash.  Then I find a share and nicehash say hey good job you!  You get a star that's worth 1k hash rate.  Find another one and I'll raise that but if you don't find another one within 5 minutes I'm putting you back down in the penalty box back down to 0 hash rate.  I don't know what the exact numbers are or the exact timing but that's what's happening to me if I compare my hash rate for cryptonight between nicehash and say dwarfpool.  My rigs will get counted for 1k of hash for say 3/4 the time and zero for the remaining which gives me 75% of my actual hash rate.  Now if my rigs were a faster say 5k and I miss an expected share not that big of a deal because like you said it will average out when I find an extra share but it will only drop to 4k hash rate calculated for that time.  The times I get 6k will make up for that bad luck portion.  Unfortunately though in my scenario the likelihood of me finding two blocks instead of one in the given amount of time at the nicehash difficulty is extremely rare so my average never picks back up.  So for the small miners or CPU miners I found it not worth it to mine cryptonight at nicehash.  Maybe others would have better luck.  I was hoping to find a XMR Proxy that would work with nicehash so I could pool all my small rigs into one larger looking rig but I couldn't find any.