Although the fight has already done and gone, I'll post here what I posted on the video (though i will admit, this was posted before I saw any of the w14p2 where it's revealed the fight occurred at the end): Tinker's crossbows.
Not sure which version of tinkers is in the pack you're using, but if it's the latest one (which after seeing Sjin use javelins, it is the one I was thinking of), you can use some of that beautiful railcraft steel you managed to make before the farmhands got to you in the smeltery to make a tinker's crossbow. Use the steel to form the bow part, then a short trip to the nether to get some flamestring (flamescar spiders and their many, many babbies) for the bowstring, some paper for the binding and some slime crystal for the body and you basically have a very durable minecraftian sniper rifle that's pretty upgradeable. Add a bunch of netherquartz to a steel tipped/steel bodied/feather fletching bolt and you've got a highly accurate weapon that rips through armor like a hot knife through butter. If you want you can even add some pistons to the crossbow itself to knockback any idiot who tries to close the distance and redstone to shorten the automatic reload time.
Then shoot them again once the crossbow's done pulling it's string back for another shot. Heck I think you can even add the cleaver's beheading property to the bolts with one of the upgrades, removing their heads upon killing them with a long range injection of cold, uncaring, revenge-fueled steel.
I mention this because on my single player game I did some tests with a crossbow similar to the one I mentioned, only with a wooden stock instead of a slime crystal stock (The stock only affects overall durability and slime crystal is a high durability material, so anything can do for that part, really) and it was highly accurate, consistently hitting a Balkon's Weapon Mod training dummy (saw it wiggle and got a hit noise) at 40 blocks away after targeting the head part of the 2x1 block punching bag.
Another interesting thing to note is that this weapon seems to pickup damage when you shoot it at a distance, I can one-shot pigmen from afar after a few upgrades but when upclose it doesn't pickup enough speed to get the kill.
What made me think of bringing this up as the Railbros ranged weapon of choice is that Steel came up as the best material for the one-shot sniper's crossbow after testing in both the bow construction and the bolt, which due to the incredible weight of it and the speed it picks up gives it great armor penetration capabilities. The knockback came to me after a mod compatibility caused my tinker weapons to gain weapon XP and automatically enchant itself with upgrades after constant use and it just got knockback, which came in very useful when i got mobbed in the Nether to push back the spiders, pigmen and other high HP mobs that couldn't be one shotted from up close. They all got 2-shotted though.
So look at making one of these sick headhunting steel railbows, it's a fun weapon.