Game Mechanics: Shaman Melee Skill Ups

[Seritaph]

Hey there,

My main is a shaman I'm leveling, currently 13. I've been soloing orc troopers who con blue in everfrost for several days. Melee skills are 1HB, 2HB and Piercing. I hadn't noticed a discrepancy in skill ups until level 12. Each level I could get 5 points of skill up. When I hit level 12, they froze at 52 (should have gone to 65), and now at 13 it seems they've frozen at 56. I understand skill ups can come slowly, but these seem locked in.

Isn't the formula (level * 5) + 5? Perhaps I'm mistaken. Some insight would be nice. Thanks much.