I know this pack is rather old and the forums hasn't been posted on in a while, but is anyone else having problems with bow zombies causing lag? They never lose agro, so when they can't get to me in my base, they lag my game immensely. This has killed me countless times due to me trying to kill the bow zombies, because my game catches up when the zombies can get to me, and a bunch of zombies jump forward.
A couple of things you could try: Find which mod adds them and disable them in the configs. You may need to do a kill command to get rid of the existing bow zombies.
Set up the area where the zombies like to congregate with some MFR Grinders or punji sticks, or whatever is in the pack that works to kill them. If they're dying they certainly can't maintain aggro for long.
Light up areas where they're known to spawn and light up to the range of loaded chunks of your base.
If you've got an already existing mob trap perhaps there is a way to funnel their pathfinding aggro into it. Exploit anything that works to get them to come to traps you already have.
You could try pouring hot lava on them or hitting them with splash potions that damage them, if you don't care about the mob drops.
Build a spot where you can swing at their feet without them getting to you, you may want to insert a half slab to stop smaller mobs from getting through.
Hope some of that helps, I don't know for sure if it all would work in that Minecraft version but there should be ways of getting a handle on the situation. Use your imagination!
I don't remember if Tinker's Construct is in the pack but if it is, build yourself an overpowered bow that can outrange them and shoot them all dead from afar.
OR any bow that is in the pack and works to kill them.