The same has been happening to me for the last three days (working fine before that). Also in NSW, Australia with Optus. I thought it might be the weather as well, but my ping is fine and I've not had issues playing Overwatch or streaming, etc.

Sometimes I can sit in the goblet and craft fine, or practice on striking dummies fine and it only lags for around five seconds every 5-10mins or so. But other times I get a 90002 error within a few minutes. I always have an issue with dungeons/instances though.

Since 4th of June I've been disconnected 100% from every instance within a few minutes of getting in (sometimes instantly). The odd thing is when I ping, it shows a stable 235~275 (which is usual) even while I'm in the middle of being disconnected and frozen in game (not so usual). There might be one or two packets lost out of fifty, but with how I'm disconnecting it really should be higher than that?

Aether data centre, Balmung.