Everything imo seems pretty balanced.. Not a fan of dice bag + Mith seeds, was never a fan of gambling in rsps xD
The only thing I don't really like is the GWD portal making you skip kill count. I think donators get a decent amount of benefits in regards to getting double kill count per kill. Maybe instead you can increase the amount of kc per donator rank instead of just bypassing the KC.
In regards to the high level skilling area, I think those are fine for regular players. Maybe can put some restrictions on Iron men / Hardcore? Like they can't use the ores, trees, fishing spots stall etc. At that point it turns to p2w for Ironman considering you don't have to go out to wildy and risk anything for high valuables anymore and kinda defeats the purpose.
As Sharingan said, all chins besides Black would be fine in the zone.. Make some sort of perk for black chins instead maybe idk.
As a suggestion, maybe a personal Donator slayer master that gives out the same tasks as Duradel and Krystilia but makes them even more monsters to kill (scaling with donator rank and the slayer rewards extension reward in slayer shop)
As for the pet shop for Gwd Pets, if they are purchasable I think changing their appearance would be better so that it doesnt match the one thats dropped, someone who gets it as a drop looks different than someone who just buys it with outright cash.
Just my two sense.. Will update if I have more ideas! Glad to see a donator zone is going to be added <3