As the Griffin is currently, there is no reason for it to need Extraordinary Kibble. I know that it was probably because Griffin is a magical creature, but it doesn't make any sense balance-wise. (The same probably goes for Megalania although I'm not focusing about it in this suggestion)
And the Snow Owl has Griffin's travelling, and a variety of very useful abilities. Even though it doesn't manage to surpass Griffin's battling at base level some breeding and a high quality saddle easily compensates this (both Griffin doesn't have) Also, Snow Owl is super easy to tame compared to the Griffin. And sadly Snow Owl has taken away a lot of need for the Griffin.
Suggestions for Griffin if keeping it require Extraordinary Kibble:
First of all make it harder to tame without Kibble. These suggestions would make Griffin powerful than now, not to mention that it would justify the effort needed to get the kibble
Add Fire abilities. That would make it more powerful and "magical" and thus justify the required kibble. There are a lot of room for thinking. Setting a target on Fire with a dive swipe, leaving a trail of Fire on diving, immunity to Fire Wyvern breath, immunity (permanent or for a few seconds) to Lava, keeping the rider heated in cold environments to name a few.
Bring back the pre-nerf Griffin. It would require some tweaking as that Griffin was OP, but I think it would be viable after making it harder to tame without Kibble.
I didn't add the saddle and breeding because I'm not sure how it would impact the balance. Ideas of someone more experienced would be appreciated.
Note that adding all of this could make Griffin ridiculously powerful, so developers, please pick what you need to make it balanced.
Or, just reduce the Griffin's kibble requirement, I think Superior would be optimal. Still people would probably go for the Snow Owl, so add some extra abilities without making it OP if you could.
Additions to the list or any thoughts, ideas are welcome, and thank you for reading.