I also only have V4.4 of Disk Warrior...don't need to upgrade it, unless V4.4 becomes incompatible with a future version of the Mac OS. (Emphasis added)
Current Systems:
Mid 2013 13" MacBook Air with 251 gig Samsung SSD
Late 2012 Mac Mini with 256 gig Samsung 840 Pro SSD
Using OS 10.11.3 on both (Emphasis added)
Support News
09/30/2015 - DiskWarrior 4 version 4.4 is Not Compatible with OS X 10.11 El Capitan
DiskWarrior 4 version 4.4 is not compatible with OS X 10.11 or later. To restore complete functionality and to gain additional features, please upgrade to DiskWarrior 5. (Emphasis added)
Edit: Unless, of course, you're aware of something that I haven't run across.