Concerning RotaryCraft and it's first party addons:
Yes, RotaryCraft's everything can be crafted, but it's progression is much MUCH different from "Let's make the next tier more and more expensive!" It focuses more on infrastructure to power X to get going than having enough energy to power Y once in order to get god material. Sure, you can build a pulse jet furnace right off the bat; but you can't run the dang thing because A: you need jet fuel and B: you need enough instantaneous energy to run the thing anyway. RotaryCraft runs on real-life mechanics most of the time, so if you don't have enough oomph to run the bedrock grinder, tough luck because you just wasted 20 Buckets of lube trying to get the thing to run. Converting RF or EU or even steam to shaft power and back is costly at higher tiers. It's like IC2, but with the added benefit that you can't store the energy without doing some assemeling at first and nothing has a true "buffer."
This also goes for ReactorCraft. You need at least jet-engine infrastructue in order to make your first uranium fuel. Then you have to build this big reactor setup and take about a thousand precautions before starting the thing up and automating it. AND THEN you have to go back into it later on and insert this thingakabob to crerate the other half of the fuel for the fusion reactor that you are going to build.
And for the server owners out there: No greifer will take the time to build infrastructure to make a pulse jet furnace run, just to make it go boom. Even a sloth will stop him/her from doing it because it takes so long.
The most overpowered mod in my opinion is:
Dundun Dun dun Dun dun Dun!
Technomancy! (Specifically towards Botania)
Technomancy allows you to build this "mechanical flower" on the cheep (A small pile of manasteel, 2 iron and an eye of ender) that will generate SO MUCH MANA that even Gaia Spreaders with Velocity lenses won't get the mana out fast enough while generating.
Sure it noms power, but it generates mana in so much haste that terrasteel is not a problem anymore. I once tried it with an ultimate solar panel from Solar Expansion and the thing just cruised along, only eating half of what the solar panel generates.