Gold Spartan5:

I doubt the scarab could reach that distance. Plus it probably has no clue the base is actually there. If thats the rhino then y do we have a scorpion? The rhino looks almost Identical to it.

 

I think the Rhino is an artillery piece, like a modern Howitzer.  It probobly wouldn't do as good in a stand up fight as the Scorpion, and would have to be in the rear, where it could safely bombard the enemy.

 And I would certainly hope that the Scarab couldn't fire that far.  It would definitely make it a priority over the large number of enemies coming down the hill.