Goliath do have stealth abilities. These things are not meant to just rush into a blob straight on.
The British Bofor gets outranged by tank guns.
...and the list goes on.
I know they have stealth, they cant stealth on the entire map though. The second they leave a crater and move up to infantry on a road, boom its gone in a split second not damaging anything. British bofor gets outranged, but can simply brace, or activate its raining death ability on the at gun, or the mortar emplacement will destroy it.