Let me correct you on one point. From July 25 to September 10 is just 1.5 months, not almost 3 months. In short, they were just quiet on Patreon in August (but not necessarily idle).
So while Deviant Tech's behavior hasn't been perfect, overall I'd say it's been acceptable. It's not like they have a tier with a fixed monthly reward that they need to put out.
In any case, their last post was on September 10, which was just 21 days ago. Typical Patreon updates are monthly (DT has just been commendable with how they've often updated multiple times a month, like 6 in June and 3 in July) so I don't see that as a problem. It's only the first day of October, so I expect their October update to come later.