Well, I got good results doing so.
Look at this:
5uk 5uk 5uk 5uk 5uk 5uk 5uk 5uk 5uk 5uk 5uk 5um 5um 5um 5um 5um 5um 5uq 5uq 5uu 5uu 5uu 5uu 5uu 5uv 5uv 5uv 5uv 5uv 5uv
When calculating this deck:
Cost: 6*2 (devourer) + 6*2*-1 (devourer skill) + 2*3 + 5*4 + 6*5 = 56
Pillars: 11
QI=5,09
However when playing this deck, you will find yourself a lot of times stuck with useless quanta (you easily get 30+ darkness quanta).
That is why I tweaked it a little to:
5uk 5uk 5uk 5uk 5uk 5uk 5uk 5uk 5um 5um 5um 5um 5um 5um 5up 5up 5uq 5uq 5uq 5uu 5uu 5uu 5uu 5uu 5uv 5uv 5uv 5uv 5uv 5uv
This one has much better results, but when calculating your way, you will find a quanta index of:
Cost: 6*2 + 6*2*-1 + 2*3 + 3*3 + 5*4 + 6*5 = 65
Pillars = 8
QI = 8,125
This suggest you will always be short on quanta, but I didn't encounter any problems (well, only the real bad draws, but on average, it worked fine).
When calculating my way, you will find:
Cost: 6*2 + 2*3 + 3*3 + 5*4 + 6*5 = 77
'Pillars' = 8+6=14
QI = 5,5
This number is a lot closer to the truth. This deck is not pretty fast, so your quanta index can be a little higher than 5 (mentioned earlier), and 5,5 is what it seams like, comparing to others.
Another note: when counting my mark, I count it as 2,5 pillar, when it is my only source of that elements quanta (like here).
Most people will feel the mark is enough to use the skills of the devourers and the gargoyles, but when counting it as a normal pillar you will find a quanta index of 12. When counting it a 2,5 pillar, you get a QI of 4,8 which is what is looks like. (same applies for speed poison for example, with 6 freezes and 6 chrysoara's on you mark only).
I count it as 2 pillars when there are only a not many pillars (less than 5) of that element, and as 1,5 pillars when there are a lot more (like in monodecks), because the lonely little mark will be relatively less effective when there are also pillars around.