As it stands, I have one Raider with Dark Lance and three with diss. I just wanted a bit more anti-tank and that Raider has Incubi with it. Thus, the point of that Raider is too soften-or try to-the potential charge target. However, if I don't run that, I bring all diss. The anti-infantry is too valuable and ninth seems more favorable to infantry and assaults with the minimum requirement for a table. Especially, with how powerful White Scar bike squads are going to be if you are on a shorter table.
Against bikes, I would prefer Diss than DL.
Side note: This potentially means that Reavers are going to be better than they are now.