When you play Kadregrin does it see itself as a Mighty unit?

Yes, Kadregrin can count itself as a Mighty unit.

According to the official RiftJudge FAQ: Q: Does Kadregrin draw for itself? A: Ruling: Yes, Kadregrin can count itself.

Additionally, per Rule 708, a unit "is Mighty" as long as its Might is 5 or greater. When Kadregrin enters play, if its Might is 5 or greater, it satisfies this condition and is counted by its own ability.