Like I said before I did the math and I'm pretty sure that a DK in medium armor will be able to tank all master dungeons because you don't get much more tanky if you go with full heavy armor.
Sorry for the DP, but I forgot to include this thought:
I actually think that the 3% base regen won't be modified through extra % regen, but that all the +flat regen will be modified by further +% regen. You feel me?
3%+(X*Y%) where X is the flat regen you have and Y is 1+the percent of extra regen you get.
For example, if you have 100 stamina you'll automatically have 3/second. If you also have +10 regen from something, then you'll have 13/second. But, if you have something that gives +50% stamina regen then you'd have 3+(10*1.5) for 18.
I think it's the opposit. That the hp reg(%) only influences the base HP reg and that the hp reg(fix amount) doesn't get effected by it.
But it could also be that all get's boosted.