highest level attribute? + rate my nec

What is the highest possible attribute level? My guild members told me it was 16, but does that include awaken the blood, or items that skill by percent chance?

Also, I want to make a necro that specialized in blood magic. Here's what I'm thinking:

nec/mes
blood: 12, soul reaping: 10, inspiration: 8
awaken the blood, vampiric touch, vampire gaze, touch of agony, life siphon, soul leech {E}, channeling, well of blood

I'm sure there are better elites out there, but I'm having a hard time choosing. I suppose blood is power would be the best choice, but it doesn't really fit my character concept - I want to be an in your face tank/damage dealer, not a support (hence, the touch attacks).

12 (+3 sup rune) (+1 headpiece) (+2 Awaken The Blood) (+1 20% focus item)

= 19

I might be missing something.

also it works for elems; replace awaken the blood with glyph of elemental power

But does increasing attributes up to as high as 19 brings effect? Skills has a set of low to high end range of effects (e.g. damage, duration). What level of attributes do these skill maximum effect capped at?

you can reach 20 in an attribute.
12 (+3 sup rune) (+1 headpiece) (+2 Awaken The Blood) (+1 20% focus item) (+1 20% weapon mod) = 20

I have a necro who can do this but actually hitting 20 is a rarity.