Tor does not help regarding resiliency. We are sometimes discussing integrating Tor but mostly think it's better to have Orbot or similar Tor proxy and use it from delta chat. If you want to discuss this further please consider using https://support.delta.chat

we got reports that delta works when signal didn't but it's notoriously hard to nail exactly why something works/doesn't work. Delta generally deals relatively well with network throttling, does indefinite DNS caching, and has pervasive support for shadowsocks and socks5 proxies. It also helps to be able to use email servers inside the NaN.

I see. I live in Iran and I could understand why it works. People can rely on existing email servers in Iran when the government had totally blocked the Internet (but not the Intranet) in Iran.
However, my main pain point with Delta Chat, and the reason I don't use it anymore was that it is effectively blocked by any ISP that blocks SMTP ports (that is, my university). It is also much easier to block than other messengers in time of crisis, unless it uses normal TLS on port 443.