Are you sure you're getting a skill increase?
I tested this. No experience increase with the Blood of the North. On the PC you can easily test by entering the consold commands:
tdt
sdt 10
Then you can see exactly how much experience you have for each skill, with a number not a bar. If I cast the Blood of the North there is no increase. If I cast a Heal Minor Wounds spell I get a small increase.
I've also checked the wiki that confirms, and I see no dispute on the wiki discussion page.
If it is increasing for you, then maybe it is mod related?
I'm on a PS3 using the GOTY Edition.
I created a High Elf without Restoration as a Primary and it had a starting value of 10. I went to an Aeylid Well and started casting Blood of the North. I would check every several casts and I could see that the red line was moving. It moved slowly but it moved.
My level 13 Orc started off with no red in the Restoration line, and now he has some. He doesn't cast spells, just Blood of the North, on a very rare occasion the two special powers from the Tower Stone (forgot what they are called. One is a Lock spell, the other increases Armorer temporarily.) I've never picked up any books that would increase Restoration... that would raise it a whole level though, and Restoration is at 25 still.
I have to admit that Restoration's progression has been super slow, but it's there. Originally there was no red in the Restoration line, and now there is.