Actually the robots only require your group to kill and convert 5 total. Not 5 for each member of the group. I have grouped with guildmates and had one killing the wretch guys for mana remnants while I killed and converted the robots. He got credit for my conversions.

Also only one has to collect 4 remnants. If your group is together when you "charge" the crystal. Then all get credit because that is the objective.