So, I checked out your armoury... on the basis of that and what you write here, I am guessing you're making some pretty fundamental mistakes in your rotation; your choice of gems also leaves a little to be desired, and 2/3 glyphs are sub-optimal. Your spec looks solid, with the exception of taking 3/3 morbidity over 3/3 improved icy touch; this can only be justified if you have another tank class (with a fully talented attack speed slow) constantly hitting the same thing as you... I doubt this is the case. However, this is of course a mitigation rather than threat quibble, so somewhat off at a tangent relative to the substance of your post.
Your post and glyphs suggest to me you're relying on obliterate and death and decay for threat. This is definitely suboptimal as blood; obliterate won't hit all that hard, and will also consume diseases (a huge no-no). Death and decay is a rune hog and inefficient for single target tanking.
In place of obliterate you should be using death strike - same rune cost, but it won't consume the diseases, and you'll also get the heal (and threat for it). Switch the oblit glyph for the death strike one for maximum effect; you'll tend to have a lot of rp as blood as there isn't much space in your rotation for rp dumps, so this adds a good chunk of damage to an already big hit.
Your rotation should look like this (first line is the first set of runes, second line is the second when you have death runes available):
IT PS DS HS HS
DS HS HS HS HS
Since rp will rarely be an issue in blood spec, it's pretty safe to macro rune strike into all of these abilities.
The other option is to use the glyph of disease as your third glyph, in which case you can refresh diseases with a single blood rune instead of a frost and an unholy - this means swapping a heart strike for a death strike on all but the first run-through of the first line (unless diseases fall off because you had to leave melee range for some reason).
As a final note: stop gemming for parry. Your initial post suggested you thought this was a threat stat... it's not, except for the tiny benefit of a slight hastening of your melee swing (I think Satorri posted something about this on the theorycrafting board recently). Your red slots, assuming you want to make the socket bonus, should be filled with expertise/stamina gems for threat (expertise is close to twice as good threat wise as hit for blood specs until you're at 26 expertise, at which point it's pretty much equal, but with the added bonus that you're reducing boss parries and thus the frequency of parryhasted attacks). Don't gem for strength. If you want avoidance, gem dodge/stam; agi/stam is also pretty attractive because of the amour and (melee) crit provided, but is slightly inferior to straight dodge for avoidance.