yes I totally agree that for a game with boss fights designed around dodging AOE it needs to be precise and the way to go is to parse the position event based i.e. per damage that may be taken by the AOE.
If they designed their whole thing around a synchronous timer (in which case they should rework their whole infrastructure if they want to keep this game running for more than a few years) the only easy solution I can imagine would be to probe more frequently i.e. per 100ms or so, certainly less than the average lag of a client.
They should invest in the new servers or whatever, the players shouldn't be asked to cope with it. That said, it can be coped with if you are not also having a bad internet connection. Since all major boss fights are scripted with little variation you can memorize the patterns and move preemptively.

Also, never use an action when you are moving away from AOE, because that will cause another position update delay.