I agree with Xinef that a 'once ready-ed creature cannot be re-ready-ed'
Dive 2x in a turn is fine (we already had that, due to TU), but once anything after that begins to step into scary zones.
If it is a SoR+TU+Dive combo that is "over powered", doesn't deserve to be a bit? Fallen Druid+Otyugh+Graveyard, or FD+FFQ+Anubis, or whatever else "OP Combo" that most decks run is more or less the same number of cards. I think if a wind/aether deck was able to stall long enough to pull off a multiple TU dive trick, a single SoR makes them a bit more powerful, but nothing game breaking.
It will only make them faster, due to creature control if nothing else (not having to wait that turn in a standoff with otyughs). In a cruel irony, the otyugh doesn't have to be on the field for the opposing rainbow now either.
Once a creature also poses a new risk-reward tradeoff with dive. Do you wait a turn for a the 2x dive, or use it immediately in fear of a hasted otyugh? I highly support Xinef's nerf suggestion.