The mobs use the vanilly item drop system. What material do you think problematic? They don't really drop too valuable stuff? Or things already dropping from other mobs?
I just looked through the source and this mod does an instakill code in it's sword? That is stupid. Techguns has it's own damage system and some other damage hacks may no longer work. I think in that case the compatibility needs to be on the other side. But Techguns has no API yet, so ... not for now.
Well some of the drops that are alarming are as follows:
* Gunpowder - Due to drop rates and nature of the mobs its much easier to obtain than from a Creeper.
* Leather - Sometimes finding a Cow is difficult and this makes it a common item, Additionally makes Cow farms obsolete as soon as you have a generic Mob Farm.
* Bread/Wheat - Mob farm.
* Redstone - Redstone can be fairly hard to come by earlier game and it being more common can cause issue. Additionally this makes any form of redstone acquisition other than from drops obsolete as soon as you have a Mob farm, this isn't as much of an issue with the Witch due to its muddied loot list however even with the Witch its a problem but not a problem early game.
* Iron Ingot - Although normal Zombies and the like can drop this its an extremely low chance (0.8%), again this is an issue with mob farms.
* Coal - Mob Farms.
There's potentially more but I have not done more testing than that. I understand based on what the mobs are that its kind of the point that they drop those materials, however I think a good config option for this without actually giving a full "pick what you want and what you dont" config setup would be is just a config option that makes all "Zombie", "Zombie Pigman", "Skeleton" and the likes counterparts in your mod drop only what their Vanilla versions can drop (Example: Zombie miner only being able to drop 0-2 Rotten Flesh, 1 Iron ingot (0.8% Chance), 1 Potato (0.8% Chance) and 1 Carrot (0.8% Chance)). I know that somewhat goes against the design of some of the mobs but for people like me concerned about how the mobs would affect the overall game in both early game and automation I think it would be very nice. Don't get me wrong I love the mod, just concerned about this singular thing (I honestly don't care too much about the Avaritia support and more this than anything since for me this is make or break).
On the sword's side:
The idea of the sword is to be an overall goal for the game and the end all melee-range weapon. This is a goal due to its extreme cost which is based on the mods you have installed; it takes all of the highest tier materials from all of the mods it supports that you have installed and makes you use a ton of them. Since I do not want to spam, heres a pastebin of what it costs to make the Sword for me minus the materials from other mods: http://pastebin.com/U16GdmVY
(In all honesty, your not really going to get to this point without months of work and I think the Sword at that point deserves to kill everything).