DutchGrown's LUI13 is quite mild. Didn't really dig it myself, but it was a huge producer and the smoke is really mellow.
but yes of course yield, smell and taste are bonuses.
Sheer potency is really the only 'no no'.
I don't have a particular taste or smell i am looking for, i know there are many different 'flavours'.
I just feel that most people are looking for 'the best', meaning strongest.
It might seem a bit backwards looking for milder strains.