Voidsense

OK, I've been meaning to ask this... why take EF at 6? With RI DB and Gloom fighting 3 yellows at a time (i.e. door missions) just about runs out my End by the end of the fight. I haven't faught any bosses yet and RI scales (I think) so is EF better on Reds? In my limited experiance when inside on a door mission if RI drops I die.