FWIW, if one (as I do) always run a tmux instance on top of whatever X terminal one launches, neither the lack of scrollback buffer nor the double-click-and-drag selection should be on the TODO list, since these features are moot granted one uses tmux. In fact, I'd prefer they be treated as bloat.
You can't class tmux as suckless. I tried it and the amount of options and commands etc. was intimidating!
It's a point though, do we need a suckless screen replacement? If you use dwm you don't need it but lately I've been looking into cwm/tmux instead.
Jon.