Not only do wars.rogues not have to worry about SP though, our holy counterparts the ret pally do not need to worry as there is no holy resistance

I've only really played DKs in PvP since cata (not including the occasional run of leading my 4 shams with an unholy DK in LK :P) so I'm new to the whole spell pen thing. How much of your damage in PvP is done by death coil and diseases? Is the shadow portion of SS affected by spell pen? Considering how awesome strength is for unholy (ie. more valuable than hit even before cap) I would've thought it'd be better to grab it whenever possible? Obviously the cloak chant is a no brainer as there isn't a str one, but surely you should gem str over spell pen regardless of cap?