Legislation notwithstanding, it doesn't seem that QR were unreasonable, they got you on next flight to SIN, and delay was only 5 hours on about 14-15 hours of travel, and some modest food vouchers were provided. Sometimes cough happens, despite beast endeavours, and we all prefer to be in a situation where airlines operate conservatively with respect to weather and aircraft faults.
From what I've read, the EU legislation was originally framed in response to certain be-harped airlines and their ilk, which provided nothing for severely delayed passengers, and would often even fly pax into nearby airports and expect them to fend for themselves on the ground in getting to destinations several hundred km away. Idea was to get the airlines to be fairer and more reasonable, but in enacting legislation its scope was widened and is very much a capture all, although reading on FT it seems many airlines do their utmost to deny claims.