Since 2.0.0 is "coming soon" (don't any of you dare ask for an ETA!), I have a few balance suggestions for consideration. All of my suggestions pertain to the early game, since that is the part I have played (repeatedly).
Lobber (AKA Lobster) Farming
A couple of weeks ago, Thorgan8 posted the design for a simple, low-tech, automated
Lobber Farm. This set up, which requires nothing more than a couple clay buckets and some quicksand, gives the player a renewable supply of blaze powder, magma cream, magma charges, and, most importantly, coal. This eliminates the necessity of dangerous early game coal mining, circumventing a core difficulty component of the modpack. Apparently lobbers can also be used to generate blood in the smeltery.
My suggested change is to reduce or eliminate all lobber drops, with the exception of magma charges.
Quicksand
Quicksand, added by Biomes O' Plenty, is a very powerful block for trap construction and base defense. Mobs will attempt to path over it, get stuck, and eventually suffocate and drop items which can easily be collected, providing a danger free source of bones and rotten flesh, among various other drops, and disposing of the various dawn resistant mobs. I have also heard that a quicksand moat is sufficient to foil Hostile Worlds invaders, though I have not tested that myself. Combined with a spawner secured within a roguelike, and quicksand provides a quick set up means of farming most mob resources.
I have several possible changes to suggest. If it is easily possible, it may be best to disable quicksand from generating, preventing it from being easily available from the very start. If you disable generation but do not want to completely remove quicksand, you could consider adding a crafting recipe for it, either behind some tech level, or with something inconvenient like sand + water bucket + slimeball. If you can't stop BoP from generating quicksand, another possibility it to put it on the grief list, making it worthless for base defense. Unfortunately, adding naturally generating blocks to the grief list is not ideal.
Instant-growing Dye Trees and Harvestcraft Trees
Saplings of both Project Red dye trees and Harvestcraft fruit trees grow instantly with a single application of bonemeal. Dye trees will grow this a random wood type, giving the player access to every vanilla wood from the safety of their base. More egregiously, Harvestcraft trees grow with immature fruit, which can be harvested by breaking it with an axe. This allows a (slightly labor intensive) way to turn bonemeal directly into food at a highly favorable rate (3-5 pieces of fruit per), in addition to the wood.
If it is not possible to make these trees require multiple applications of bonemeal, then I have a couple suggestions for balancing them. I suggest disabling dye trees, if it is possible. The resource they add (dyes of every color) are accessible by other, more difficult means in the game. Harvestcraft trees play a more important role, and I would be sad to see them go. One way of limiting the utility of bonemeal, chop, and replant farming of Harvestcraft trees is to make the sapling recipes more expensive. My suggestion would be to have them require a piece of mutandis in addition to the base sapling and piece of fruit. This fits thematically, and limits the throughput without moving trees too far down the tech tree.