Does Gordrakks removal of cover ability stay? It doesn't say until end of turn. The "within" and "units" part is very important. It means that if you get lucky you can practically remove all the the cover on the table. Including garrisons.
" In addition, after this model makes a charge move, you can pick 1 terrain feature within 1" of this model and roll a number of dice equal to the Massively Destructive Bulk value on this model’s damage table. If any of the dice are a 6, units no longer receive the cover modifier to their save rolls for being on or within that terrain feature. "