Yes there are logs of everything. No they won't necessarily give it to you. The first time my ten man group did Full House (which isn't hard at all but takes forever and our holy priest likes to smite LDW scarily close to breaking mana shield) it simply did not give us the achievement. We put in a ticket and they were like "lul yeah we've gotten that a lot but we can't give you the achieve" even though there are logs of a certain number of add spawns and what died and therefore what was still up. Just ended up getting it the next week.
But good luck and grats on KS. :P