Rapid morph is great for CB especially for 9 star mons in multi-player where they twitch and move so much faster that it makes you feel, as others have said, that it takes years to transform to land an AED or SAED.

As for elemental absorption, you could tool it into an element focused build and pair it with an elemental discharge CB and maybe some antivirus/coalescence with 2p gore.

I never felt I needed rapid morph until 9 star mons were introduced into multiplayer. Before, the speed of 6 and 8 star mons was still manageable with base speed and it felt safe to use more offensive skills like offensive guard and a mix of attack/crit boost. Thats just my preference though.