Yeah, most low- to mid-security sites don't have guards that can challenge even starting shadowrunners, nor are they meant to. Those guards are their to patrol, observe and rattle doorknobs. If they see trolls with heavy machine guns entering the premises they aren't going to engage, they're going to call in the HTR teams and hunker down on held action behind hard cover. Most security guards are there to delay and contain the runners until SWAT can get there.
This is usually at least a few minutes for most physical teams, although HTR hackers and mages (in astral, with spirits) can respond in combat turns.
