What weight ? Heroics are so easy it really doesn´t matter if someone does suboptimal DPS. If those 3 minutes the run takes longer really annoy you so much then run die daily with your guild mates.
Oh and do you really propose he should gear up on valor gear so that he can run heroics ? You do know they are there to gear up freshly dinged lv 90 chars, do you ? If you are annoyed with people getting gear then don´t do LFG groups.