How is the "N" in PPLNS chosen? 2xDiff appears to make no sense - OR - Why are Scrypt share difficulties off by a factor of 65536?
An AntMiner L3+ submits a share at difficulty ~150,000 (which counts as a share value of 150,000 then) every ~15 seconds, so in 3 minutes, that one AntMiner has already filled the whole "N" of 900,000x2=1,800,000. That would, in reverse, mean that I would expect to mine a BitConnect block every 90 seconds on average, with one AntMiner, which is of course not true.


I don't think that is how shares are counted. According to this Bitcointalk post,


  When a share is submitted, assign to it a score of 1/D, where D is the difficulty at the time the share is submitted.


So in your scenario, when your AntMiner L3+ submits a share, that share is assigned a score of 1/900000, so its "share value" is 2, not 150000.