I've driven through this intersection a few times. The DFO entries are poorly designed, and I think what adds to the issue is that this is a fast roundabout with relatively poor visibility. It's designed in such a way that you can travel through it (too) quickly, and because of the poor design of the entries, people get confused about which lane they need to be in. Cars can disappear quite easily behind the infrastructure holding up HBD as well, and with the speed of the roundabout, cars which have disappeared behind pillars/ramps can come at you quite quickly. You're then in a situation where people who visit the DFOs infrequently are unfamiliar with the layout, and they're contending with regulars who do know what they're doing.
The diverging diamond interchange sounds like an interesting notion. From what I've seen, implementations in Queensland seem to have gone quite well. Wasn't there one being constructed at Varsity Lakes as well?
Cheers,