Did i miss something or did mortar trap get nerfed to only being able to place 1 at a time? i remember clearly being able to put 2 before expansion.
You could never place more than one at a time, but they do get increased limits to 2 and 3 at max level and max ultimate level. There are items which increase the limit as well, so you can eventually get 5 or 6 with a 1s cooldown.