Theres an exp/loot bonus at the end of a strike. A lvl 3 Dreg will give 20 exp the same as a lvl 24 Dreg. Vandals will give I think it was 35 exp regardless of level. So I kill everything for added loot and exp. One guy even thanked me earlier saying he got a Legendary in the mail from the strike. He ran through and got it mailed to him because I killed the mobs. If you need speed runs do the lvl 12 Nexus strike. Speed run some low lvls through it but I'll be grinding my lvl 24 strikes.