have you tried something like:
make a formula
{table.producta} + {table.productb} + {table.productc}
group by this formula and go from there...you might still get dupes, if there are dupes in the data, but you can work on a suppression formula like:
{table.producta} = prior(table.producta)
and
{table.productb} = prior(table.productb)
and
{table.productc} = prior(table.productc)
HTH