John, the only times to avoid fishing in Bali are June, July and August, with October to April being absolute best.
May I ask if you are planning a dedicated long haul fishing trip here? If so, you might want to think a bit more about that. My advice is always that Bali is a great place to fish if you are coming on holiday anyway, or as a cheap and very convenient fishing trip from elsewhere in Southeast Asia. The fishing though is a bit too inconsistent to warrant a dedicated long haul fishing trip. There are far better places in Indonesia for that.
I don't know of any spots where you can realistically target GTs above 10 kgs from shore. The spots for big GTs are around the offshore island of Nusa Penida which requires a boat trip. When the fishing in "on" there it is truly top quality.
Jigging for big Doggies is very tough here. There are plenty of monsters for sure (I and many others see them when diving!) but they are almost unbelievably difficult to catch. Smaller ones yes and jigging for these is very possible along with Amberjack, Ruby Snapper etc.