:5d|9d|16d|28d
Is how to put four single commands in a row. But better turn it around:
:28d|16d|9d|5d
To keep the numbering constant.
A more flexible way is to use vimscript. Squeezed on one line this is:
:for n in [28,16,9,5] | call deletebufline("%",n,n) | endfor