So by sending nothing, you end up sending everything? Lol what a strange fix, but hey, if it works 😊 I stress tested using feedback routing on my single machine setup using 40 vipro instances all running through mir, several CPU hungry guitar vsts double tracked to separate amp sims, 5 instances of massive on ultra settings, 20 kontakt instruments (mainly chris hein horns, session horns pro and discovery series) and the garritan cfx on full settings playing something like 50 notes at a time with the sustain pedal. All of them were routed (in vipro) to illusion, a fusion ir that takes a fair amount of CPU. I loaded each midi track with as many notes and keyswitches as I could fit in. On a single machine, 4.5ghz quad core processor, at 128 buffer I got a few clicks here and there but nothing ultra distracting. At 512 buffer the clicks disappeared completely. I should also mention I have a very entry level audio interface. I don't know how this compares to your template and hardware, but I hope it helps. VEP is just amazing, even on a single machine setup. EDIT: It also occurs to me that if feedback routing does indeed increase CPU load, then the very thing it enables you to do - freeze individual tracks - can be done to decrease CPU load! Win win :)
It is not a fix, it is a trick to use while we are waiting for a real fix, but I think that doing an empty routing it shouldn't cost so much to apply.
I have an 8 core CPU (16 threads) with 64 GB of ram so this sounds great. I use a lot of automations so I'm keeping buffer size at 512 and I was starting to have some UI lags with big projects, this is why I'm trying to move the CPU load from Reaper to VEP.
Well, it seems that it works great, so I think I shouldn't have performance problems using feedback routing with my configuration. I don't like to freeze tracks because while I'm composing I keep editing tracks many times so for me it would be a continuous freeze/unfreeze process.