In their last interlude final server, where spoiling was not easy not hard, they put A grade for donate 1 week after server opening. Now imagine you farmed 1 week, spoiled, crafted, waited the new week for mammon so you can unseal set and.. BOOM A grade added in shop for around 6€ or so.
You get VIP = extra exp/sp/drop/spoil/fame/Epaulette. Then donation for autoloot, more buffs(improveds), global TP, vitality replenish - all for donation.
Clan eggs, clan rep is very bad idea for donation.. it should be hard to obtain
SubQ after 1 or 2 weeks available, same with varka lvl1-2, this will all remove the PVP for spots that's supposed to be there.
It's just my opinion that donation is a bit overtuned, many people will join regardless of that. There are always + and - for everything.