If you have dual spec on your DK simply switch to frost and hop in frost presence. While still frost spec switch to blood presence then activate your other spec whether it be blood/unholy spec. Now you should have the increased health that the improved frost presence gave you.
As long as you dont die or switch presences you will keep the health increase. I sit around 33000 health in my dps build![]()
(buffed that is)
EDIT: repost ftl