Yes, that combo is right.
The 4-hour event dragons are nicknamed as the “ultra-rare-commons”. They are difficult, but not impossible to get through breeding.
However, for this, and the Leaderboard events, you have the option of crafting them. Always begin asking your neighbors for the necessary parts as soon as the event starts, even while you are attempting to breed it. This way, if you can’t breed it, you can at least craft it early.