Modified bug title, Ive managed to isolate this bug down to an interaction between evocation_illagers and zombie_pigman, restored the original json files + a targetting tweak to make sure it wasn't my behavior pack to blame. From my observations it is something to do with the evocation_fang hitting a zombie pigman, causing an edge case that crashes the game.

1.11.3 crash:

Faulting application name: Minecraft.Windows.exe, version: 1.2.15.0, time stamp: 0x5cda1049
Faulting module name: Minecraft.Windows.exe, version: 1.2.15.0, time stamp: 0x5cda1049
Exception code: 0xc0000005
Fault offset: 0x0000000000f75af0
Faulting process id: 0x3e4
Faulting application start time: 0x01d51459adfeae01
Faulting application path: C:\Program Files\WindowsApps\Microsoft.MinecraftUWP_1.11.301.0_x64__8wekyb3d8bbwe\Minecraft.Windows.exe
Faulting module path: C:\Program Files\WindowsApps\Microsoft.MinecraftUWP_1.11.301.0_x64__8wekyb3d8bbwe\Minecraft.Windows.exe
Report Id: 2fb69af7-6ad1-4e28-ab6e-7b34b176cb64
Faulting package full name: Microsoft.MinecraftUWP_1.11.301.0_x64__8wekyb3d8bbwe
Faulting package-relative application ID: App

1.11.4 crash:

Faulting application name: Minecraft.Windows.exe, version: 1.2.15.0, time stamp: 0x5ce32765
Faulting module name: Minecraft.Windows.exe, version: 1.2.15.0, time stamp: 0x5ce32765
Exception code: 0xc0000005
Fault offset: 0x0000000000f76fa0
Faulting process id: 0x1c68
Faulting application start time: 0x01d5145ac1edfcd2
Faulting application path: C:\Program Files\WindowsApps\Microsoft.MinecraftUWP_1.11.402.0_x64__8wekyb3d8bbwe\Minecraft.Windows.exe
Faulting module path: C:\Program Files\WindowsApps\Microsoft.MinecraftUWP_1.11.402.0_x64__8wekyb3d8bbwe\Minecraft.Windows.exe
Report Id: d9b4603f-9267-4087-b640-928eda43f2ca
Faulting package full name: Microsoft.MinecraftUWP_1.11.402.0_x64__8wekyb3d8bbwe
Faulting package-relative application ID: App

I can provide more info about the behavior packs and isolate problem behaviors if required.