Which focus takes over when healing? Or do both work together?

I have Chailak Hide Mask with 35% healing increase
I have Wrapped Glass Shard with 15% mana savings.

The Chaliak Mask is your healing focus, and the wrapped glass shard is your beneficial mana preservation. So to answer your question your mask and primary would both work together, in that your healing focus helps how much you heal and the primary helps with your benefical mana preservation. But also looking at your magelo your qvic arms have a higher healing focus so I am pretty sure your arms are your healing focus, not your mask. Correct me if iam wrong here hehe. I pretty sure that the higher percentage focus will be used not the lower percentage.

ok, that helps. But then for my arms I'd have to NOT use the ancient heal since the 45% on the arms caps at level 68 spells.

So I might be better off using regular 68 level Chloro or even NI.

45-(4.5*2) = 36%. Qvic arms work better on ancient heal than your mask.

Ethierway, for your purposes I'ld say Si is the best bet for your primary heal.

someone needs to write a "How Foci Work" and sticky it.
not it.

not it

/wouldn't get it right anyway

Oh, and I don't have SI.

/still not it

Kaylani's and Kamion's posts pretty much explain how foci work. AFAIK (and IANAE), foci stack with each other as long as they are different kinds. That is to say, your increased healing and decreased mana cost foci will stack, but my 45% increased healing and my 40% increased healing do not make me an 85% better healer. The game picks the better of the two; whichever one will benefit you more (taking into account the max level and penalty for the focus). If they are different foci, they will stack...least I'm pretty sure.