move to an mboxing guild if your server has one
I would agree with the 4 rolls out of 5 but this is usually what happened to me when I was in a non-mboxing guild.
someone in the guild asks for a special run and I let them loot everything because I think it's a one time event, in particular if you are running someones lowbie through an instance.
Then the person has so much fun they want to run with you all the time ( go figure, they got 100% of the loot for 1/5 the work ).
This invariably expands (usually within one day) to them wanting to twink their toon in all possible instances at my expense.
The best thing that happened to me was to join an mboxing guild. nobody needs run-throughs or twinking and it's just nice to be among like minded players.