DL's should be done while you are fresh and at your strongest mentally and physically, therefore at the start of your back workout. You can get too sloppy with your form at the end. You maybe a little weaker on some other back exercises such as low rows and one arm rows, but you shouldn't be any weaker on lat movements like pulldowns. Keep asking questions TNT, don't ever be discouraged by the losers out there, listen to the answers that make sense and let the smartass remarks drive you to be better than the assholes who make them.