Primary cause of T5 Divebomb failures

[Sove92]

With the divebombs, the marker above a player tells you nothing, merely who it's targeting. You don't know which direction it's coming from, nor the resulting size of the attack. For all the player knows, it's as wide as a house and swoops in from all angles.

You can actually see where the dive is coming from, and Twintania will always dive from the same location on that particular spot. So if you stand in center of the arena and get targeted, Twintania will dive from a predetermined location at you, and that's where she always dives from if a party member in the middle is targeted. There isn't really anything strange about the mechanic. If it was as random as you are claiming, the ditch method wouldn't work. The ditch is popular because it causes about 75% of the dive's width to go outside the arena, that way you need to move less, giving you enough time to get back in the original position.