engi is just a bad class besides last lol if u want to slow it down and run single sacks that's fine, otherwise if u run sniper they can solo into u or engi/heavy they can kill the rest of your team super easily cuz ur so slow
edit: seven and old HRG played very slow and methodically which is a good way to play in high pressure matches, now teams are generally more coordinated and the meta has developed to do 2 man sacks regularly