A correction on the Blood Tap.
The 2nd tier talent in Blood, reduces this to a 30 second cooldown.
As a Frost spec, Blood Tap is once a minute.

Still, it allows for three sets of Howling Blasts, as the opener instead of two sets.

I'd probably rather have the Unholy talent, where if a disease is decursed the rune (Frost) refreshes.
Not to mention, the first tier of Unholy is better overall for this spec... 9% spell hit, will really help Howling Blast.