I'm afraid I just don't get what's 'hard' there: A DSU will never overflow and can be attached through storage busses. There's multiple ways to set up the feed to the boilers (depending on what you feed them with) but again with level emitters it's completely trivial.
But the setup you described will never retain any wood for building OR will only start building after some minimum number is reached. It cannot both store and produce outputs at the same time.
Again, I still don't understand what's hard or 'bad' about this: you use level emitters to 'do' something with certain items based on how much you have of them. You can export to whatever machine or storage or crafter you want. It just works.
You end up with massive fields of expensive blocks just to keep your stuff under control.
Sorry but what? AE is completely awesome for any form of processing. I have a whole story of my based dedicated to processing whatever comes in (and I have a lot coming in; ores, bee products, wood, etc.) and it all works purely based on AE.
For reasons described. It is the most expensive and one of the least controllable systems for farm output processing I have at my disposal.
But if you have concrete examples of what you find difficult to achieve in AE I'd love to hear them.
Help me out here, please:
The spruce farm example is a good one. I'd like to both begins to store spruce planks for building and process spruce wood into charcoal for burning. So I want a DSU full of planks and DSU full of charcoal. Were I to naively wire this with import and export busses, I will
radically overproduce planks because my powered furnace will turn out results more slowly than my sawmill will. So I'd prefer to send more wood down the charcoal processing line so that I produce charcoal faster, since 1 wood = 6 planks anyways and the sawmill runs fast. This is not an unreasonable request.
And then:
I would like to convert 90% of my MFR rubber in plastic sheets and 9% as raw plastic, and 1% as raw rubber for sticky pistons. If any one of these resources overfills a DSU, I'd like to start dumping raw rubber out.
My opinion of AE is that it's great, but instead of being a solution to storage problems it exchanges one set of problems for another. It is great to have the autocrafting, but barrel sorting systems tend to be better about handling overflow.