I think you may be missing the accomplishment that TPL has achieved here. Most mods that i have played gate the high end equipment behind scarce resources. Even Vanilia did that: the best gear took diamonds and potions needed nether resources. Which is why mods like magic crops (and sometimes bees) are considered OP to the point game breaking, there is nothing to limit your access to unlimited amounts of super tools.
With Regrowth TPL has achieved an entirely new form of progression. With the exception of early seed/essence repeatables (which can be bypassed with enough dungeon/mineshaft exploration) he even avoids old HQM stand by of: "turn in crazy amounts of X to get this device".
Instead he has modified the recipes to integrate the mods together gating progression behind the various mods mechanics and created quests to guide you thru this while telling a story. Getting iron at all requires understanding and using the core of agricraft and botania. Once you have access to it it's role as a restriction largely over. Reducing the quantity from the recipe or removing the smeltery/crucible/dust/native cluster ore multiplication simply slows down the real thing you should be doing once you have iron: exploring the unlocked mechanics.
Examples:
One that is hit upon in this thread several times: Real progress in Thaumcraft requires (baring some luck with the polywhatever charm) alter powered cauldron rituals in witchery, which requires elven portal progress in botania. Blood magic requires another step in witchery with circle magic.
The real gem and proof that TPL has planned this pack well past the point the quest currently stop:
On the tech side a basic AE2 setup requires (beyond the certus quest that can be bypassed with exploration or the botania loot flower) making components using machines from BC, RC, Mek, Forestry, Mariculture and, in 0.80, gardenstuff. A super sized AE2 setup here isn't being gated or slowed by the rarity of iron or even diamonds, it's held up by the complexity of the modified recipes. It is true that once you set up and integrate automation for each of the machines from the various mods there is nothing preventing you from mass producing everything in crazy quantities. But once you get to that point you have completed one of TPL's stated goals for the pack: learning, using, and mastering these lesser used mods. And to be honest if you can set that up I want you to be able to mass produce the parts of an AE2 Spatial Storage system just to see what you can do with it.
A secondary point,closer to the resource generation itself, is that the returns from the 8 essence donut recipes are setup to maintain resource relative rarity: Coal gets you 12, iron 8. All the way down to ardite giving one. Sure you can make iron "harder" by halving the return from the recipe but now Ardite is twice as common relative to iron as it was.
That second point however doesn't matter because with only basic automation my 3X7 ardite patch produced thousands of blocks of ardite while i slept saturday(why did i do this? golems look like they are having so much fun as they run around leaving one idle makes me feel bad). You can't make the essence recipe any harder (well not much making the donut a square i guess) and removing the smeltery doubling would have resulted in a smaller "thousands of blocks" but still leave me with "Building with the block because of it's cool texture" quantities.
So i'm "rich" because i have thousands of blocks of diamonds and emeralds. It won't do me any good in AE2 if i can't figure out the BC laser table or in Blood Magic if I can't figure out a Witchery circle spell. And that is what makes this mod pack so fun and unique: not that we can use all these mods, but that we have to to make any "progress".