Strange, I just restarted spacemacs and now 'ci(' works.
In the previous session I've changed some settings and
that seems to have irritated spacemacs.
't' is for html tags so pressing 'cit' anywhere on '<width>280</width>' will do what you're expecting. :)
I only just noticed this now, but `dit` and `cit` only works in html (and other web derived modes) in spacemacs. I guess some of the stuff only gets set up on the major modes.