As much as I love st, I had to stop using it recently. When using a bitmap font in tmux, large amounts of text sent to stdout bring my computer to a standstill. X is using 100% of a single core. I've switched to gnome-terminal and the issue is gone.
This, along with the generally accepted notion that Gnome Terminal is one of the slowest with output, puts the whole minimalism idea under a serious question. "Do one thing, but do it well ", the saying goes.
Really? Generally accepted by who? My unscientific personal tests show that Gnome Terminal is the fastest and lightest VTE.