I finally got my Island Thunderscale! I've been dutifully grinding every day for several hours the last week (and the three weeks previous when we had those back to back Jorundalls on the map rotation) I haven't seen any Thunderscales on the island today at all, (Sunday) (or any since Tuesday)
I decided to try leveling my low level alts via islands instead of spamming Mythic on my main. If nothing else it made it less frustrating when the mount didn't drop because at least I was still getting XP. Got it on my 115 lvl Warlock on Normal. I didn't see any drakes at all, but then we got stuck on the beach when the 2nd and 3rd waves came in. I also started eating any fruit I saw along my travels. No idea if that helped at all but at this point, it doesn't hurt to try.
It makes me wonder if the 'difficulty' chance / drop rate is in any way related to your toon's level vs the level of the scenario. Maybe that's why so many people have mentioned getting it on Normal vs getting it on Mythic (when they are likely on a max level toon with high stats)
Good luck to those of you still hunting!
