Zentress critical damage vs offense for raiding

So clearly ventress would normally fall into the category of wanting critical damage mod sets over offense. But what about rampage which gives 15% offense stacking per kill? In raids that quickly compounds, but is it and at what point is it enough to say the extra base offense to be compounded is better than critical damage bonuses? For simplicity, assume ventress is always at 100% critical chance; She gets there basically with the first wave of minions killed in aat (thinking of p3-4).