Hello,
i have upgraded xfce4-terminal to 0.8.0 version which uses vte3 and now command
xdotool type --window "16777446" "hello"
don't produce any output in desired window (also don't produce any error).
Xfce developers ToZ and Igor identified it as vte3 problem (command also don't work in their gnome-terminal).

xdotool type "hello" 
works in actual active xfce4-terminal window (produces output).

commands:
xdotool windowactivate "16777446";xdotool type --window "16777446" "hello"
only activates desired window, but does not provide output

possible workaround is 
xdotool windowactivate 69206019; xdotool type --window getactivewindow "hello"
but it slows down scripts and is not safe to use in parallel...

my local (archlinux) version of vte3 is 0.46.0+5+g398a3f8-1

we discussed it also here:
http://forum.xfce.org/viewtopic.php?pid=43470#p43470
https://bugzilla.xfce.org/show_bug.cgi?id=12926

Thanks.
Martin