My own RNG solution
Standard coffers drop often enough that the RNG aspect is totally fine for them, no issue there. (Opened hundreds myself, still no ticket, but it’s only a few days into a month long event. There is no cause for issue here).
On the rich coffers, I don’t believe there is necessarily anything wrong with the implementation of gambling for skins, however these boxes should perhaps contain a tooltip displaying the % chance to receive tickets. It does seem that too many fools are rolling the dice without actually understanding that they are by no means guaranteed a skin, nevertheless the common opinion that all players are entitled to receive these skins is unreasonable.
The same mentality with which you approach a real life casino must remain when considering “rich” coffer purchases: If you are unprepared to lose, do not gamble.