Those are really subjective.. if the users (or remote systems) don't complain, its fast enough...
Generally I'd say that >10% of swap being used (all the time) may be a problem, but not critical unless it keeps going up.
If swap does keep increasing, then eventually you'll get major slowdown (thrashing) and ultimately, when swap is full, the oomkiller will start killing processes.
Another rough rule of thumb is keep disks no more than 80% full, otherwise any heavier than usual load will fill them up (=> crash) before you get a chance to fix the issue.
For CPU, iirc, if all 3 values are >5 that's a bit high, >10 (consistently) is usually regarded as a bad thing, but keep in mind my first sentence....