Having a couple expendable vultures on aggo seems to help with wyverns attacking your base. The wyvern chases them up high enough that they eventually despawn. Seems the vulture always attacking from above keeps them flying higher and higher. This tactic has saved my base twice from rogue wyverns.
The best way to level up a Giga on Rag is to get a bunch of wyverns to follow you on your griffin/ptera, then dismount you’re flyer above the Giga, then get on your Giga and absolutely destroy them. This got my Giga 26 levels from 3 wyverns.