IMO the best way to increase your deadlift is to hit up good mornings, hard. Both power arch and conventional.
I'm not a fan of deadlifting very frequently, mainly because I have found this is the more difficult and slower way to go up in weight. I have much gotten better results on my conventional deads from GHRs, rack deads (not too high off the floor), and good mornings. Hamstring work is HUGE!! If you really want to increase your deads stay away from the leg curl machine and stick to the SLDLs from a deficit, SLDLs, and GHRs.