Hi Rob,
I am not sure if I understand fully the note you wrote. Anyway, the one
thing which is not that correct: nobody uses hydrogen electrode since it is
terribly inconvenient. NHE (normal hydrogen electorde) indeed is the
standard one but people normaly use only Ag/AgCl or Hg/Hg2Cl2 plus there are
some like antimony electrode etc. plus double junction electrode. You can
always say something about NHE but do not claim that it is the most
important one or amoung most usefull.

Secondly, you do not need reference electrode under one of the following
reason:
1. working electrode is much smaller that the reference one so the reference
electrode is not loaded.
2. in some amperometric systems where you control current directly from
current source
3. probably in systems with very low current density at the electrode
surface so the reference electrode is again not loaded

P.